M-Audio makes a bunch of USB based audio modules. Depends on what you want to do though. Most of their products are aimed at professional/semi-professional/hobbyists musicians who have a requirement for higher quality DACs and lower digital audio latency than the onboard sound chips. Modules such as the Audiophile 24/96 USB will do the job and then some, but is probably overkill for listening to mp3's, they won't really improve games at all. And it costs $199 most places. The Sonica will improve cd's and dvd's, and costs $59 at newegg. that might work.