Ok, back from a loooong session of gaming, gotta admit with headphones i can hardly tell the difference in SS2 and css, fear is a bit more noticeable as is UT2k4 with xfi patch. Quake 4 with OAL patch and 2142 are noticeable though, your surroundings don't sound very realistic, in 2142 if a grenade blows up on your left you hear it though the left speaker very loudly and next to nothing out of the right and it feels artificial.
In css, ss2 and fear sound was very good to the point where i found i had to concentrate to tell the difference between the two, that is probably due to the quality of the card and the games audio engine over crappy on-board audio solutions. When it came to games that were optimised for the xfi's gaming capabilities the gap was noticeable with poor sound-to-location representation in 2142, q4 and party ut(with xfi patch).
With 7.1 speakers it copes rather well, like the headphones, the extra speakers help out the reduced feature list however i am inclined to believe that these card do support some form of eax, the same level that other cards are legally allowed to support (3 or 2?) however this is not advertised.
So a quick low-down. For music, video's and films the card is fantastic and mops the floor with realtek. In games the line between the two is blurred slightly due to the lack of latest and greatest in eax and hardware processing but it is not to any degree bad, working to a close level that my elite pro does in a variety of games on headphones and 7.1 speakers.
Against your on-board stuff this card is miles better, the quality of sound is crisp, detailed and of generally good quality when paired up with some good speakers or headphones.
Against a higher end xfi it begins to loose in the games department with slightly poorer sound representation in games but still beating realtek soundcards in games by a long shot in the quality department.
Audio creation seemed to be ok but it seems to be cpu calculated if you try to do anything that would use the xfi chip to its max.
All in all:
Music = 8/10
Films & video = 8.5/10
Unoptimised games, ie css = 7/10
optimised games, ie. 2142 = 5.5/10
value for money = 8.5/10
problems = none, what so ever!
Good job creative!