I've been getting more and more into indie rock and have found great new bands, but, not enough space on a iPod. 
 
so i got the x1 and the flexible swappable microSD is awesome. THIS IS EASIER THEN A IPOD SYNCING! 
(drag and drop is great!)
 
I've already used 7 of 8gb of the card (just to start out with testing my music, I'm going to get a 32gb or higher card next)
 
im wanting to change some of the AAC formats to WAV, FLAC or OGG latter on. 
 
i mainly listen to classic rock like Grateful Dead, Hendrix, Who, Led Zeppelin, ECT... or new rock like the Black Keys.
 
coming from a iPod, some music (for now, if it needs to be -broken in-) kinda sounds different. 
some music like the grateful dead sounds better and detailed then a iPod, but then some like zeppelin kinda sounds farther away and not as detailed.
but then, other songs do sound fine. 
 
is there a "break in" period?
 
over all I'm probably am going to get the x5ii (i don't know when) latter on. 

the x11i are great, 
it adds some bass but not that much more, but its great with details.
i wish it had better low bass that you can "feel" in stead of just the tone. 
(value wise, its a 50/50 because of the low amount of materials used and light it is, i wish there was better built drivers, kinda)
 
i mainly use my Schiit Audio Valhalla2 and Bifrost Delta Sigma:
i listened to Pink Floyd:TIME, it sounded great and i could hear even more background sounds and detail
THEN, 
i listened to some modern rock: black keys, Hippo Campus, Tame Impala. 
they all sounded great with hearing even  more details.
 
the range is better then the s3 and i could tell right away
(i still have to break them in more) 
 
 
 
 
 
 
 
all in all, 
i was kinda hesitant to go with klipsch because i heard "some" negative reviews towards the customer service and durability BUT,
i mentioned a personal preference about "magnets" to klipsch and they switched the standard magnetic clamp case with the pouch, 
that type of customer service is great! i like to buy from companies that will listen and help their customers, 
ill for sure will be buying towers from klipsch as well.(latter)

my first Schiit was the Modi and Magni and they were great and added quality and "space" to my music, 
 
so, i then got the Valhalla2 and its added even more detail, quality and "space".
 
I've first used the Valhalla2 with Modi, and it worked fine. 
the sound opens up more then with Magni and more detail. 
 
i would like if there was a easier way of getting different tubes to experiment wiith, through Schiit, BUT, the stock tubes are great.
 
I'm using some IEMs (Klipsch s3, i know i need better IEMs)(i can't use headphones because of strong magnets) but the Valhalla2 is great on low gain, and, 
actually my IEMs don't get warm vs using the Magni, i always think there a little warm, but the V2 dosnt heat them up at all, 
 
i don't even have to turn the volume up much, theres just so much more detail that i want to listen to the detail and not crank my music like i normally do. 
 
Schiit is fantastic and i have 4 products from them 
Magni, Modi, Valhalla2, Bifrost Delta Sigma

the new Bifrost Delta Sigma is great, 
i first got the Modi and Magni then after 1 and a half years i got the Valhalla2 and wanted a better Dac,
so i waited for the Schiit event for the Bifrost to be updated, then went for it!
verses my modi using it with my Valhalla2, i noticed noise, BUT, now with the Bifrost (DS) I have yet to year noise. 
I'm actually using some klipsch IEMs (g3) before the s4i, I NEED BETTER IEMs I KNOW,-im limited to IEMs because i can't get by strong magnets.
I'm going to possibly get Klipsch X11i, Westone or Shure next.
 
the audio quality i put SLIGHTLY lower because some tracks off youtube (HQ or FLAC files if they even were)  didn't sound that well at first, but that might be because it needs to warm up more (break in).
 
 
overall, 
Schiit is a great company with great support for their customers and the Bifrost DS is my 4th purchase.
its really has added more detail to my music and a even wider sound range and "space" the Valhalla2 is a great compliment to the BIfrost (as well as with Modi)