I tried the v-moda m100 a few months ago when I purchased it and deciding between them and the hd 650. In the end I kept the 650, these headphones are without a doubt pretty overpriced for the sound quality.
 
Pros: The m100 is pretty stylish is it one of the most stylish heaphones out there, build quality seems somewhat solid though I am not a big fan of those metal hinges it just seems a bit delicate for my tastes. These headphones are without a doubt for bass heads they are pretty v-shaped but it also seems like it is lacking or a bit rolled off on the treble. Bass extension is great but just a tad bit farty and uncontrolled (stock pads).
 
Cons: The m100 is pretty overpriced for what it does perhaps not Bose overpriced but around there. My kevlar cable had these little white wires coming out of it, after a week of use and to be honest the sound quality is not that great. The mids are really recessed, with the bass basically overwhelming them bass it is not as controlled or defined as it should be it sounds bloated and slightly farty. The soundstage is extremely closed in there is basically no sound stage with these headphones. Due most likely to the slight roll off on the treble, this headphone is missing a ton of detail and resolution in the mids. The bass doesn't help much as it overpowers them. Basically for what this headphone retails for $300 it is not worth it at all, at that price point you are better off getting a deal on an hd 650 or 600 and if you just care about bass heavy music I would suggest the he-400 instead. If you want something portable the momentum sounds better than this heck even the m50 is better.

I decided to write this review because I have done some research and it turns out there isn't that many reviews on this particular headphone.The majority of the music I listen to is alternative, rock, classic rock, Sinatra mostly mid centric music. Now this was my very first grado headphone that I have ever purchased. Note, if you are looking for a headphone that does great with every genre these grado's are certainly not it. These headphones are meant for a very specific taste/ears they excel with certain genres and lack in others, it is safe to assume that these headphones aren't for everyone.
 
Pros: I have to say there are some things that the grado's do very well and those are the mids. They sound forward and aggressive sometimes a bit too aggressive and you really feel like the singer is in front of you. Vocals sound clear and so do instruments though there isn't much instrument separation. The sound stage is really narrow which causes everything to sound really close together now depending on who you are you might like or hate this.
 
Cons: There are a few things that the 325i's don't do as well such as the bass and micro details, and they can suffer from an overly harsh treble. Now I don't mind treble I actually feel like headphones today need more treble the hd-650 comes to mind. But I can say that the grado's took this to an extreme, this isn't a big deal on some recordings but when you hear something that has alot of treble and you are listening at semi to loud volumes the treble can be borderline painful. Grado's I feel encourage listening at loud volumes, because that is when the vocals are perfect, however when you hear the highs you have to immediately turn the volume down, I realized this when I was listening to a few tracks where the treble kicks in a little late into the song. The bass to me is really lacking, it isn't as pronounced as I would like to be. One of the 325i's weaknesses is the micro details, I tested this out by listening to various recordings that feature small little details that in some of the cheaper headphones you don't pick out as easily. I couldn't hear these on the grado's it might be because everything feels so aggressive and overwhelming at times.
 
Verdict: So are the 325i's for you? Well that depends if you are sensitive to treble I would say don't even consider these. However if you are someone who listens to a lot of rock and roll and you love treble and aren't very sensitive to it then I would recommend these specifically to you. These headphones are geared to the enthusiast who doesn't want anything toned down, basically someone who is looking to get the same sound signature you would get at a rock concert. You won't hear all the little details because it will be extremely loud but you will hear the vocals and mids extremely clear and treble will be just as lively and loud.

I still recall the day I placed my order for the He-400's, I waited with anticipation and days seemed to last an eternity. But the moment they arrived and I connected the dac to my computer, I was severely disappointed. Needless to say I listened to them for about 30 minutes before I put them back in the box and left them there. My father is also pretty passionate about audio and knew beforehand that I had ordered these headphones. When he asked about them I just told him I'm returning them, he was curious as to why so I hooked them up for him. He listened to them and looked at me and said why don't you like these?
 
They sound extremely clear and detailed. I explained to him that I was expecting them to sound incredible. That same day I processed my return but the company I bought them for offers a 60 day money back guarantee. So I decided I would give them another try and eventually the sound grew on me, and I began to appreciate the clarity and the separation of the instruments. The amount of detail I noticed subtle things in my music that I had never heard before and I had never experience sound stage this good.
 
However for the many great things that the He-400's do right they also have their flaws. My biggest gripes with these headphones for me personally were the build quality and the comfort. These headphones were probably the most uncomfortable pair of headphones I have ever owned. They are heavy and produce a lot of clamping pressure. In all honesty I could not use these headphones for more than 30 minutes before I started to feel strong discomfort. The other fault lies in build quality, in my opinion these headphones don’t look or feel like $400 dollar headphones.