X-Fi Music has CMSS-3D, Xonar - Dolby Headphone.
Few weeks ago I had both these cards (X-Fi Fatal1ty + Xonar D1) in my PC.
CMSS-3D works quite good in my opinion. While listening to music it is horrible ofc, but in games... Really helpful.
When I turned on Dolby Headphone sound suddenly become very distorted. It makes you feel/hear like you were in a deep well (again - MY OPINION).
You should remeber that Xonar D1 is almost completely neutral (I'd say it offers a litte bright sound). X-Fi Music, Gamer, Fatal1ty and so on are quite 'warm' cards. Fatal1ty wasn't a very good combination for me with Creative Aurvana Live (which are also warm headphones). CAL performed much better with D1.
Today I've got AKG k240 Studio@Xonar D1 (neutral+neutral) and I really like it. I get quite good positioning in Battlefield 3 with 'HF' mode on (Dolby, EAX etc disabled).
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Wait, you wrote X-Fi Xtreme Audio, not Music. My mistake. Xtreme Audio is the worst desktop version of X-Fi (just emulate most of the effects).
I'd definitely choose the D1.
Edited by Devil - 1/2/12 at 6:32am