What's the best USB audio interface?


I want to set up a dedicated music server on an old book-sized PC, digital out to an outboard DAC (a cal Gamma, but it could just as well later be another DAC) and then onwards through a headphone amp to cans.

So the PC will serve as the digital source or occasionally as a CD transport. There won't be any recording/input needs - and USB will be the way to go to bypass the onboard sound card (no free PCI slots anyways).

In searching for a suitable USB audio interface for this purpose, I've run across references to M-Audio/Midiman (sonica and others), Roland/Edirol UA 30 (or 3(D)), Xitel, Ego-Sys, Audiotrak - many more... the market seems to be moving fast ... I'm lost in the thickets.

I'm not looking for a one-off solution, consensus of any sort, nor do I expect to get great sound w/o a proper transport, better DAC etc. I'd be grateful if any a-goners could share their relevant experience (success? trials & tribulations?).

Thanks,
agonanon
I have the M-Audio Sonica. I like it a lot. It runs to a Monarchy DIP and then a ART DI/O DAC and then to my preamp. Music sounds good.

The Sonica requires Windows XP or 2000.

John
The m-audio description of the sonica mentions Win XP, 2000 but also Apple's OS X. But I wonder whether the sonica might still work with linux kernel 2.4 and above which has USB support - OS X is Unix-based as far as I know. I think it may be to some degree widespread that USB devices can be used with Un*x, even if this OS is not officially supported. May be just wishful thinking tho.
I am using an older computer as my music server. I am currently using a AMD K6 522 mHZ CPU with 256 MB SDRAM to host about 4000 mp3s (legal downloads from www.emusic.com) and a bunch of live shows in the lossless SHN format. I have several older used hard drives and a PCI IDE controller card which controls the three hard drives and the one CD-ROM (a generic Creative 24x). The computer is also networked to a faster CPU with even more music (more SHN files). I have a generic 2 MB video card. My OS is WinXP Pro. I don't have any other hardware (no PCI soundcard or modem). This computer is basically a bunch of old parts that I had laying around.

My media player is Foobar which uses the kernel streaming to move the music out the USB port. Foobar sounds much better than the other media players I have tried (WinAmp, FreeAmp, MusicMatch, MS Media Player) and uses far less resources. It only works with the XP/NT. Foobar also has fewer features than most media players. It is a slim player and not full of bloat like many of the others.

Attached is a review of the Sonica from ExtremeTech:
http://www.extremetech.com/article2/0,3973,662385,00.asp

Also, I have not found drivers for the Sonica except for NT/XP drivers.

Hope this helps.

John
Definitely helpful. Foobar sounds interesting, on the order of 0.5mb of code - small and has a v. active developer community going for it; merits closer inspection.

http://foobar2000.hydrogenaudio.org/
I just read that the Xitel Hi-Fi link only needs USB drivers--no hardware specific drivers. It should work fine with just about any OS.