I mostly use high-end headphones (unless everyone is out of the house) and on the X-fi I use Entertainment mode at 96hz output, eq flat, Crystalizer on but at minimum, CMSS set for virtual3d and speakers are set for 2/2.1 I find I get the best overall sound in music and games and I can still hear good sound in music and also get the virtual 5.1 from my headphones. I dont bother with the game mode as, imo, it sounds awful. The only time I use audio creation mode is to capture itune songs and convert them to wav then mp3 so I can use it in a REAL mp3 player and not the ipod.
in audio creation mode I keep everything off or flat to get the cleanest capture.