Get the X-fi, you will be disappointed by the Audigy2 when all the new games start coming out (like UT2007). It has EAX 5.0 and it's virtual headphone surround is the best I've ever heard.
Quake 4, Doom 3, BF2 and FEAR already take advantage of the X-fi, UT2007 will follow, as will anything using the unreal 3 engine.
BUT, just get the xtrememusic, the fatal1ty is a waste of money.
so, umm, err yeah