MP3's come off sound card as a digital output into my Denon AVR 1800 which does the decoding, CD's from a Cambridge Audio Azur 640C v2, DVD's from Cambridge Audio DVD 300. All goes into the denon as a digital input (except for the CD player for obvious reasons) and then gets thrown out of the Denon's preouts into a Rotel RB976 6 channel power amp (runs in bridge mode for a mono amp for each front speaker 150W per channel ) and sent to Kef Concerto 1 floorstand speakers, Kef Cresta centre and Kef Cresta 1 rears. Only ever use 5.1 for films, strictly stereo for music, ruins the soundstage otherwise.
Oh yeah got the Xbox going into it as well. One proper hifi for everything, can't abide computer speakers.