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