Check out the Soundblaster lineup of outboard soundcards/DACs. They connect to the the PC by USB, most with USB 1.1 and do not require Asio driver. They do stereo, 5.1 and some do 7.1. 24 bit/92 Hz DACs. S/N ratios over 100 dB (cause its outside the internal crap from the PC). List prices range from $50 to over $200. www.soundblaster.com.
I am using the Soundblaster Live!, RCA analog connects into Sherwood 100w x 6.1 receiver, B & W LM1 desk top speakers and small Velodyne sub. I listen mostly to the online radio stations while working on my PC. The nearfield stereo sound is awesome. Almost like headphones.