Saw nobody had answered this yet. I have one and I wrote this little mini review/ commentary on head fi that might at least partly answer your questions:
Fiio X5
First a declaration - I'm kind of a lapsed audiophile - I have pretty serious kit in my lounge but definitely got to a point when I felt that enough was enough and I really could not tell the difference between, say, a decently made £30 cable and something costing £200 or more. It never occurred to me to take portable audio that seriously, ambient noise and tiny earphones seemed doomed to make it something to pass the time on trains and aeroplanes rather than something for seriously focussed listening.
To that end I've used most apple products and a sanza clip+. The latter is an extraordinary bargain and seems to be to sound just as good as the former as well as giving you some storage upgrade potential. The fact that its an extraordinary bargain seems to me though to lead to a bit of hyperbole, its great but its not magic, it has a certain clarity and a crisp sort of treble but I was never surprised by the sound. It was fine.
Anyway I acquired some Sennheiser Momentums, which I grant you is a curve ball given the previous comments, basically I won an ebay bid a silly price unexpectedly when I was just looking for something that looked good, would not fall out of my ears and would not break in five minutes. Plugging the Momentums into the Clip+ gave me a sense of what might be possible, not an utter transformation but some shafts of detail and involvement that promised more and made me rethink what kind of impact I might reasonably expect from portable audio. Oddly I did not find the same sense of possibilities with my, then, current Apple product which was an ipod mini (this will probably surprise nobody)
So my conclusion was that the player did matter, real involvement might be achievable and went on the hunt. My budget and my sense of the conditions I would realistically be using my player in led to an absolute ceiling of £300 (do people take £2000+ players on the train? Do they put it in pockets? Bloody hell!) So I chose the Fiio X5 which arrived a week ago. So here are my observations:
a) I do not hear difference in sound quality that I can consistently associated with bit rate (but I have nothing below 320) I do hear differences that I think are to do with mastering.
b) A well mastered recording can sound utterly astonishing - amazing levels of detail, tonal accuracy and a lack of congestion even on the nosiest stuff. (WARNING PROG ROCK REFERENCE One particular favourite is Pawn Hearts - for the handful of people who might know what I talking about I can hear everything that's going on in even the most psychotic parts of "plague of lighthouse keepers" and for the first time ever I have heard Robert Fripp's guitar parts)
c) The UI still has me confused - I still can't find my way around as quick as I'd like. But I think some of the complaints about it are a little bit overdone. Maybe things are helped in that I have some very long pieces on my twin 64gb cards so I have not broken the track limit.
d) When plugged in I can only "see" the card in the first slot - I have found ways around this but I assume the computer should see both - but I had endless problems getting the 64gb formatted to fat32. Currently both cards can be read in the computer if they are in slot one and both cards work fine on the player.
e) The Fiio X5 is certainly the best player I have owned, yields a genuine musical involvement quite different from my previous experience with portable audio and the twin card slots and ability to read higher amount storage cards is likely to mean it will serve me well into the future.
f) I have no comparison to offer with other "audiophile" players - Ill leave that to others. For me though the feature set alone, even assuming sound were similar across the competitors would make the Fiio the winner. I think if you come straight from Apple with no particular computer skills you might be a bit shocked by the simplicity of the interface but I don't think I should be a deal breaker.
FWIW
Graham
http://www.head-fi.org/forums/posts/edit/postId/10482971http://www.head-fi.org/t/661411/fiio-x5-thread-info-updated-on-jan-17th-2014/7500#ReplyQuote Multi