The Presonus AudioBox USB meets all of the requirements above. It is relatively inexpensive, rugged, and reliable. I can wholeheartedly recommend it, with one small reservation which may only apply to my setup.

After a move I reconnected everything, but apparently plugged the AudioBox into a different port. One of my applications (Propellerhead Reason) "lost" it, which is common with USB. However, with this unit it is necessary to uninstall the drivers. Unfortunately, there is no automated routine to do this. Last time I checked it was necessary to go into the Registry and edit it manually, which is a royal pain, and not up to Presonus' usual standard of excellence.

On the other hand, all of my other apps still see it, notably BIAB and RealBand, so this may not be an issue for you. Otherwise the thing seems to be bulletproof. Mac's recommendation of the VSL is a good one; it has some special features which you may find interesting, if it is in your budget.

"My primary musical instrument is the personal computer."