a quick google found this http://forums.techgage.com/showthread.php?p=19871
which looks like basic support under linux.
Really if your wanting an easy time use kit that's under the hardware section of the wiki. If your using other kit then you'll need to do most of the searching and testing yourself as the developers have more then enough just working on this projects code base and not having random issues with hardware that has flaky support.
I've got a Creative X-Fi card in my main rig, linux support really sucks for it so for easy of use i use my onboard, works a charm. Also if your using an External receiver that takes digital the quality of your sound card don't really matter.