Build & Usage:

Good looking, very nice feeling player, it looks like a really sold build, and it's an all-metal construction. Not much to say about it, you can check pictures. I wasn't satisfied with the overall usage of the player because of quite a few flaws. The screen isn't so good both when it comes to viewing angles, colors and resolution, it is sufficient, but again, for this kind of money (~700$) more is expected in every segment, including that. It's also a touch screen (2.4 inches 320 x 240), and it's quite small for that, especially if you have thick fingers (and most of the people interested in audio things are men, that have larger fingers than women so...). It's fairly responsive but not nearly as responsive as an average smartphone or iPod touch for example, not nearly like that but it's ok; it's responsive.
Now one of the biggest flaws with usage was that volume wheel on the side. It's ridiculous. It's so badly designed it's unbelievable. It sticks out in a really bad way, so it's fairly easy to damage it while putting the player in a pocket that volume wheel is always bugged outside of pocket so you need to put it inside carefully. It's also so sensitive that volume will adjust itself by accident inside pocket, which can be truly frustrating (when you are placing it in the pocket it will adjust as you push it down your pocket). It's really badly thought out and even tho they fixed it with the AK120 (those shields next to the volume wheel) that doesn't make the life of AK100 any easier! It's a disaster in my opinion, especially for this kind of money. You can turn off volume wheel feedback in settings but then you will just have useless wheel sticking out of the right side of player that is not doing anything. Big flaw!
The user interface is decent, for that small screen it couldn't be much better, again it's not really fast UI (I found FiiO X3 user interface to be less laggy than AK100 for example) but it's ok, you are going to listen to music anyways, who cares if it's a bit slow while changing song, not a big deal but again, for this kind of money you expect something a bit faster. This is nowhere near iPods (classic or any other) or smartphones.
It also uses 2000 mAh battery, I didn't get battery life nearly as stated (up to 16 hours) but it wasn't bad, surely it will last a bit more than using a smartphone for music.



Sound & Comparisons:

It sounds good, no distortions on high volumes, no hiss on low volumes and runs good with all kinds of headphones, but then again, if you have some really hard to drive, you might need an external amp, tho it's not that different from other similar portable players. It uses Wolfson WM8470 DAC, which is fine, a good DAC. But the problem is to me THE SAME sounding FiiO X3 has the same DAC, that very same Wolfson DAC and it costs over two times less, which is... hard to find the word! Honestly, there isn't much if any difference with this player or any decent smartphone (iPhone for example) if you use low impedance easy to drive earphones (like I do, IE80) but if you try to drive something harder to drive it certainly outdoes the smartphone. The good thing is that it has two micro SD card slots, which is rarely seen with players (even the latest Astell & Kern ones have one slot).



Summary:

Honestly, not worth it. Yes, it sounds good and looks good but the flaws are way too big, price is way too high and the competition is way too good. For literally over half the money, there are the likes of FiiO X3 with the same performance and even exact same DAC but with fewer design flaws (such as frustrating useless volume wheel and somewhat slow UI). Let alone that for the money you can get new FiiO X3 second generation and have left for mid - high end 400$ headphones/earphones, or X5, which is maybe an even better option. My conclusion is that this is an overpriced product not nearly worth the trouble and hype. Some people are sold by nice and shiny aluminum built and "premium" feel but not me. I've returned mine and bought FiiO X3, and I'm more than happy with my decision. Don't get me wrong, it's overall a decent product, it's a good player, very nicely built and good looking, with sound to back that up but for the price it's unbelievable. Not worth even half of it.

Build & Usage:

I have Sennheiser RS 130 for over eight years now (and still lasting!), which says enough about their durability, and the most fascinating thing for me is that I haven't changed the batteries even once. They use two rechargeable 600 mAh batteries, those "normal" looking ones found in a TV controller for example, not sure what kind of batteries those are exactly but you can literally buy them in a supermarket, even tho I repeat - I haven't changed them once in over eight years.
Headphones are over the ear design and come with a stylish looking dock that is used for putting your headphones when you are not wearing them, and it also charges headphones whenever batteries are not full, which is great since you don't have to think about charging, ever (never happened in over eight years for them to be empty, always charged and I never even thought about it). There are two buttons on the dock, one for choosing frequency mode (3 settings), which I also almost never used, and the other for turning 'surround' option that was nice sometimes when watching movies or playing games but not so good for listening to music. There are three small lights on the dock to indicate if headphones are on/off, charging and whether the surround option is turned on or off.
Headphones have enough range even tho ~150 meters I've read somewhere is nonsense. But at home, I was never out of range, so when I go to brush teeth in the evening for example, I leave headphones on my head even tho bathroom is quite a few meters from my room.
Headphones are made out of plastic which is nothing bad; they are durable, light and comfortable, but don't expect some supreme build like 1000$ ones. Dumping force is pretty small, so they won't be extremely secure on your head, but I found that actually useful since they are home only headphones, it's not like you'll go running around with them so that low dumping force actually makes them more comfortable for longer usage even tho not staying so secure on your head. They have on the left earpiece on/off button, and on the right earpiece, there is volume wheel and 'tune' button that seeks frequency that dock is set up to work with (if you change one of those three frequency settings you need to press that button for the headphones to find it). I found this to be useful only in one situation: I had two pairs of these headphones when I lived with my dad a couple of years ago (since headphones are over eight years old), one was for my dad, and the other was mine (still is). The problem was when we both listened to them if it was the same frequency. But thanks to those three frequency settings, we could isolate one from another so we both listen to our own things.



Sound:

Soundwise it's really hard for me to explain since I got really used to them, and I'm not quite a professional when it comes to describing sound. I could compare them with my other headphones, but it's pointless if you don't have these other so I'll try my best to describe sound but take it with caution. Overall it's not a harsh sound, not the clearest sound you've heard but pretty decent for the price. For a wireless set of headphones, there isn't a lot of hiss while the music is played; there is hiss only when you pause the music, which is kinda normal with wireless headphones like these. Highs are not harsh as I said, mid-bass is somewhat there, tho it's not so bad. Similar to most other Sennheiser headphones, I guess it's their "house sound signature" so you'll be fine with it if you like most other Sennheiser headphones in that department (mid-bass, veil or whatever you wanna call it). Bass is not overwhelming at all but it's there. Sound is not fatiguing; at least it wasn't to me. I could listen to something for hours, watch movies, or playing games without any problem. They don't isolate well at all, but again, it's for home use only so isolation shouldn't be a high priority for most people when it comes to wireless home headphones, but if you need to "escape" from the people around you or if you plan to use them at work or somewhere where is loud - be warned. Next to that a sound leak is there, so if you play something really loud if someone is in the same room they will hear what you are playing but again if you listen at normal volumes that shouldn't be much of a problem, tho be warned if you are in the same room with someone trying to sleep and you crank the volume too loud, it can get frustrating a bit, mostly because those higher frequencies are the ones that leak first which is normal. I have them for over eight years, so the sound must have changed a bit over time, of course, so take with caution my sound description.



Summary:

I paid for them ~110$ (12500 Serbian Dinar), which was, in my honest opinion a steal. Maybe not at the first look, but now over eight years, I really find them to be one of my best purchases ever. Yeah, you could most likely find even better-sounding headphones at that price, but I highly doubt it would be the better value overall. These will last a LONG time, and these are wireless and comfortable, so they are perfect "budget" headphones for home use. Well, it depends on what you consider 'budget' but 110$ I paid for them was really cheap in my opinion, especially if you look that today there are headphones for a couple of thousand dollars. I have seen now new wireless models from many companies, including new wireless Sennheiser headphones (quite a few actually) so I'm not sure if there is a better deal than these (not even sure if you can still find these somewhere since they are becoming ancient), but if you are looking for budget headphones, even if they are second-hand ones since they are so durable, I can gladly recommend these, ESPECIALLY for the price I paid for them. But again, maybe there are better deals nowadays, this was over eight years ago, I wouldn't know now so I can't guarantee it.
I also want to note that I gave them a better rating than my Sennheiser IE80 that cost three times as much for example (and sound better, even tho they are in-ear, so it's hard to compare)... which says much about my opinion on RS 130 overall.
So not the best soundwise that you can find for the price but far from the worst, and certainly a very good value overall looking at all aspects that make a headphone as a whole product: quality, durability, comfort, usage, wireless range, etc. so don't dismiss these so easily!

Pretty short review of the things that needs attention in my opinion when it comes to the IE2:
 
I paid for them around $140 here in Serbia and for the price I was disappointed. I chose IE2, when my Sony EX300 cables stopped working, because it was available in my god forsaken country Serbia where we don't have much choice except those highly commercialized brands as Bose. First that came on my mind is that there was a nice soft-ish leather-like black case, not huge but on the bigger side when it comes to in ear earphones cases which I found to be very useful since you don't have to fold cables too much. That was about everything that was good with these earphones. 
 
They just didn't sound good, first of all no isolaion at all, just like normal earbuds, while I expected it to have no real isolation (read several reviews and watched videos on YouTube of them) I didn't have an idea it would be so bad, since I got used to having the isolation on my previous earphones I forgot how bad it can be when there is none.
Completely useless earphones in the loud gym, while riding bicycle because of noise and wind, completely useless in a loud bus... you get the idea! Sound was... well ok, not extremely bad but nothing special, it was on the same level (different sound but equivalent level) as let's say my 70-80$ EX300, which are double cheaper and have isolation. They lack a bit that lowest sub bass feel, mostly due to isolation but in general they lack it, but the bass is strong overall, especially for the earbuds with no isolation, not much to say about the highs and mids, not sibilant but nothing special. 
 
Those highly advertised StayHear tips (something similar became more popular with new Beats Tour v2) were ok, 3 sizes, easily torn apart (my mid size torn while I was taking it off the earbud to test the small one) but generally soft and comfortable and it stays secure inside the ear shell, better than other in ears that have cable down design but still worse than the ones with over the ear cable design. Still, complete lack of isolation was something that I should be aware of but didn't quite expect this bad situation. 
 
My advice is to avoid these at all costs, especially when there are so many choices in this price range that literally blows away these, even so much hated from the wannabe audiophiles Beats Tour are noticeably better than IE2. Friend paid 140$ for his Vsonic GR07 that are better in every possible aspect and it is not a matter of someones opinion. Don't get me wrong, they are still better than stock earbuds you get with your smartphone, but if you can, I recommend searching further for another option.
 
EDIT:  I just saw that worldwide they are around ~110$ now which makes them more saner choice, still there are a lot better options even at 110$!

Package & Build:

FiiO X3 comes in a nice box with an adapter and micro USB cable, as well as a nice soft silicone sleeve to protect the player. It is built very nicely, has some retro touch to it since it doesn't have any wheels or touch screen, just buttons and normal, not so good, screen (but it does the job just fine). It has coax out, line out and 3.5 mm headphone jack as well as a micro USB port for charging, using as an external DAC or transferring music from PC. On the right side there is a "hold" switch that is used to block other buttons to be mistakenly pressed, though I haven't used it once since the buttons are not that sensitive, and it will never happen that you mistakenly press a button, but still there it is. On the left side there is a MicroSD card slot (you don't get a MicroSD card with the player), and the player itself is equipped with just 8 GB of memory, but who cares about that when you can get 128 GB and if not now then soon 256 GB SD card. The player is built with the combination of metal front and back and good plastic around, it looks and feels nice. It has a decent battery of 3100 mAh, and while they claim it will last ~10 hours, I get around 7-8 from it, though I'm crazy track swapper so the screen is on a lot more than an average person would have. It's also decently light at 122 grams, which might surprise some because of metal finish - it looks heavier than it is.


UI & Usage In General:

The user interface on X3 is good and it couldn't be much better if you see that it doesn't have a touch screen and/or volume wheel. It's decently fast and responsive with an exception when you have a huge size album art on your songs, then there is a delay in UI when you play or change the song; it starts playing in an instant, but the screen is frozen for a second or two till it shows the position of the song, it's not a major issue but just to note it. If you have a small size album art or no album art at all, the X3 is very fast and responsive. There is also a possibility to change the themes and make themes on your own, and it's not hard at all, several videos about it on YouTube and several posts about it here on Head-Fi. Buttons are responsive with that nice click when pressed and all the buttons, since there are only six of them have more purposes, for example if you hold back button it will display song info, and if you hold play/pause button player will turn off/on, etc. Firmware updates bring real improvements and good changes, which is really great! FiiO's support is very fast; at least it was to me, they answered me in a few hours after I sent them an email (had some random question).


24 bit talk:

Ok, first a small story here: 24-bit audio cannot sound better and it doesn't. It wasn't just randomly chosen for a CD standard that 16/44.1(48) audio; it is precise mathematics, and they considered what we could hear. 24/192 audio has more dynamic range of 144 dB (range between lowest and loudest signal, and CD audio quality has 96 dB), but humans perceive less, ~105+ dB effectively. But! Also environment noise, even with great isolation won't come lower than 10-15 dB which means the lowest signal cannot be lower than that noise (or we wouldn't hear it, it's called masking), so in a studio when they are finished with editing they compress the dynamic range, and it should be, must be, and it always is equal or less than the capability of CD (96 dB). And when people are speaking about resolution or bit depth, that manifests through that higher dynamic range and lower hiss. Hiss in 16/44.1(48) is inaudible. None of this is a matter of opinion. Audio isn't some abstract magic; it's very measurable, very proven, very tested. 24-bit is useful in a studio because it leaves editors to work well above the noise floor, and when they are done, they just compress it and it leaves space for mistakes also, as well to other several things, but for now that's it. Oh, and if someone says something like "soundstage opens up", the sound is more "clear" that is literally like you believe in dragons. Why I said this - because many people are aiming for the good players because of that "HD" audio capability, which is complete nonsense, and it is not a matter of how good someone hears or a matter of opinion. I'm sure many of the companies wouldn't even mention 24-bit audio, but when several started with that to make money others didn't have a choice because people simply started following the hype. After all just get some song from HD tracks for example (or anything similar, a lot of free promo samplers that are 24/96 or 24/192, Linn also gives often free some album) convert that very same file to 16/44.1 and enjoy your blind test, that no one ever passed and that no one can pass.


Sound & Comparisons:

Player sounds good, if you use small impedance IEMs that are sensitive (like I do, Sennheiser IE80) you won't be getting probably any benefit from having a player like this instead of a smartphone or an iPod, but if you drive some harder to drive headphones you will certainly hear the difference. There are no noticeable (at least I haven't noticed) distortions on very high volumes like I had on Nexus 5 above 90% volume, which is good and expected. It plays everything you might want: ALAC, FLAC, WAV, mp3. And till recently (firmware 3.3) it has support for playlists too and it has 5 band equalizer. DAC inside is good quality Wolfson WM8740 also found in several products of a lot higher price than X3 like Astell & Kern AK100 (mk1) that cost literally over three times more (700$ vs. X3s 200$), and it produces a good sound though not distinguishable from other modern players or latest smartphones that have well built-in DACs. I have read many reviews, and people are talking about how it has wide soundstage, some say it has narrow soundstage, some say it has good imaging, some say it has decent warmth and whatnot. I say it's nonsense; several of my friends, my father (far bigger audiophile than I am) tested it vs. the AK100, AK120, iPhone 5s, iPod classic 5th gen and Nexus 5, and imagine wonder! None of us could tell the difference with IE80, VSonic GR07, Sony EX700. (I'm just talking about IEMs now because that's what most people would use a small portable player with) When you plug in something harder to drive X3 shines in comparison to smartphones because it has a lot more powerful output (250mW on 32 ohms). Generally, better amp than smartphones.


Summary & Recommendation:

Overall a good product with a fair price of 200$, which kills all competitors in value, except maybe that new FiiO X1 of just 100$, haven't heard it though. Good looking, good sounding with as good as possible UI if you consider it's non-touch and all buttons player that is decently responsive with fair battery life (will last you more than a smartphone, that's for sure!), I gave it four stars because there is a space for improvements, they should've added a volume wheel so you can adjust volume fast and without having the player out of the pocket, the screen could be a bit better, and after all, it's hard to
value much a player next to smartphones (when it comes to the low impedance sensitive IEMs, that I mostly use) so to have five stars it REALLY needs to shine to carry an extra device in the pocket. I use it a lot as an external DAC on my PC because my sound card is bad, and there is a lot of noise coming from my PC when I connect any headphones, and I use it in a gym for example, where I never bring my phone to distract me. If you need to drive some bigger headphones, and if you have a need of an extra player, I can gladly recommend the X3 but don't get it just for the sake of hobby if you have sensitive headphones of a low impedance, you will not be gaining much, if anything.

Package:
 
Nice looking small hard leather case that is not so usable due to a lot of cable folding (when I describe the cable you'll understand why is case so useless), plenty of silicone tips of different sizes but no foam tips like with EX1000 for example.
 
 
 
Build & Comfort:
 
Earphones themselves are built pretty good, they look nice and feel pretty nice, they have magnesium body which I found to be decently light for the size (they aren't that huge but still, 16mm dynamic driver had to fit somewhere) and nice looking, nice design overall. Cables don't go over the ear and they are not replaceable which might be a deal breaker for the price (it's a good thing when a 300$ earphone stops working because of the cable and you just buy new one for 10$ instead of whole new earphones). Cables are simply extremely bad, they lasted me for around 9 months (and I took as much care as possible) and I've sent them under warranty (2 years, as usual) and got full amount of money back because they didn't have another EX700 to give me as replacement since they were discontinued I think some time ago, and they returned money pretty fast so good support on that side but still a disappointing situation. Cables are really thin and their design where one earpiece has longer cable so it goes around your neck isn't the best either in my opinion, one earpiece keeps falling down all the time even tho cable is light (due to it's thinness, not because of it's build quality or something!). But generally earphones themselves are comfortable, housing is light and it doesn't touch ears much (only the silicone tip) and the driver placed on the side is pretty good solution since it's 16mm which is like the biggest driver in any in ear earphone ever (next to 2 other Sony models and Final Audio Design Piano Forte IX/X).
 
 
 
Sound:
 
Excellent bass, just great! Honestly I haven't heard better bass on in ear headphones. It has really good sub bass, that feel... on some songs almost sound like real subwoofer speaker and not in ear headphones, I guess brain trick you there but it's really engaging. Mid bass is also decent and it doesn't interfere with mids like many other dynamic driver headphones so EX700 sound very clear, accurate overall, with a lot of details.
They have a problem tho, a huge one - highs. Highs are sibilant, piercing, deafening. Good source can fix it to some point, but if you crank volume up a bit it becomes really fatiguing and unbearable. Not only the highest freqs here... I couldn't listen to one of my favorite bands (Guns n' Roses) because Axls voice makes me deaf with them. Jazz tho and all kinds of audiophile recordings and acoustic instrumentals sounded like heaven, much much better than the Sennheiser IE80 I own for example.
Not much to say about the mids overall, clear nice sounding, bit recessed tho, but in my opinion strong point of these is excellently controlled and deep low sub bass, not overbearing but well present while the weak point is treble.
Isolation is not the best but also not the worst I've heard, it's sufficient (haven't tried foam tips tho since they don't come with earphones) - at the same level as lets say IE80 if you've heard them.
 
 
 
Summary:
 
If you are sensitive to piercing highs and like to listen at louder volumes skip these without even trying them on but if you like to listen at lower volumes, mostly at home (so you don't break awful cables that can't be replaced) relaxing music, audiophile recordings, jazz and such this might be the best choice for money you can make - very accurate and clear sounding with so great sub bass. They should be still around to buy at 250-300$ which is fair if you are good with the highs.

Package:

Nice looking but not really so convenient hard case with tight space for the cable. Most of the tips are useless; There are no mid-size foam tips (that most people use); just large and small foam and silicon tips are in all three sizes, but others are really useless (odd shape, no isolation or extremely uncomfortable). I found ear hooks to be useless as well and not so gentle on the cable since the critical point of breaking, where the cable connects to an earphone, is loose. There is also a nice cleaning tool with a screw on the other side that is used to adjust bass.



Build:

Just great! Looks great and feels good, and they seem to be very durable, the first earphones that lasted me over a year (and still lasting). Cable didn't look so good to me at first but it is very durable. When it's cold outside, it stiffens up so you can't fold the cables over the ear nicely, but in just a few minutes, it becomes softer thanks to your skin temperature. Cables are also replaceable, which is great!



Sound:

When I've read reviews about IE80, I expected them to be REALLY bassy, but they are fine. When everyone was saying for bassheads I thought they would have that deep sub-bass ''feeling'', but it's not exactly like that. They have a good amount of sub-bass and punch, but there is a lot of mid-bass (~100-200 Hz, can't exactly tell). Mid-bass is the main problem, and the reason why I didn't rate them higher than four stars. It veils the whole mid-range, which makes them much less clear earphones than they could be (tho clarity is on decent level); Some songs, especially vocal jazz (female vocals with somewhat deeper voices), just sound bad because of that, it's really not enjoyable with so much mid-bass 'veil' or how should I call it.
Isolation is not as bad as I expected when I've read reviews here but not the best as well. Foam tips can improve isolation, but it increases further that problem with mid-bass so I didn't find them to be a good solution.
IE80 has adjustable bass, just like the IE8, you can increase the bass with the small screw that is also used as a cleaning tool, but it is useless in my opinion. On minimum it has too much mid-bass, and if you increase the bass it will become impossible to listen to some genres (forget about vocal jazz, harp, rock with a lot of bass guitar, anything with the bass guitar for that matter if you turn the knob to increase the bass). I've read here about the 'tape mod' where you put the tape on the knobs that let the air in and mid-bass problem should be solved - well wasn't exactly solved but it did help a bit, reduces bass overall which leads to clearer sound and then foam tips are much saner choice than before.
I liked the highs; there is that sparkle, and they sound fun to me, maybe not so realistic all the time, but they are not too harsh or sibilant.




Summary:

Overall good sounding IEM with great build quality and not so useful accessories with one problem that can be a deal-breaker for many - mid-bass that veils mids, making them sound less clear and not so enjoyable to listen on certain songs. If you like that kind of sound and don't mind it, then it is a very good choice (after all they were top range Sennheiser at the time, can't be that bad, but if you are sensitive to it and listen to vocal music (especially with a deep voice) you might want to skip these. Price was too high at 450$ (would be 3.5 stars), but now at 300-350$, it's a pretty fair deal comparing to the competition in this price range.