I have the D2X... drivers are a bit of a PITA but seems as though its the same across all ASUS cards. I moved to ASUS from Creative because their drivers were **** so its like being between a rock and a hard place.
Got the drivers sorted though now but still have a problem where the Mic picks up a sort of buzzing sound constantly. May be due to the GPU apparently and I have moved the D2X as far away from the GPU as possible but not helped. I have configured Mumble to get rid of the background 'hum' but if I'm using Skype etc. its annoying for the other people listening to me.
HOWEVER, its a great card for listening to music, films and games on but doesn't have massive, woofing bass if that's what you require.