Lots of high quality sound cards used by professionals in mastering:
They have both 2-channel and multi-channel sound cards. I'm looking at the Audiotrak sound card myself as a decent alternative to the Audigy cards (sounds crappy), M-Audio(better), and Mad Dog Entertainment(never tried).
I use an older EGO-SYS 24/96 waveterminal sound card, and it sounds wonderful (especially compared to an Audigy sound card which i also have installed purely for game playing).
I'm planning to have a surround install in my car, and the only variable left is a software based surround sound engine (with bass management). Think of it as the software equivalent a surround sound receiver. The software should at least process most of the movie surround modes (Dolby Digital EX, DTS ES, DTS MUSIC) plus Dolby Prologic II (Movie AND MUSIC), and couple of proprietary surround modes thrown in ( Circle Surround, SRS, Meridians Trifield, etc.) Wishful thinking at this point, unfortunately, but I'm sure someone will come up with it eventually. That is the beaty of a CARPUTER because component upgrades would be just soundcards, and processor upgrades would be just software....