Strictly for gaming, I would think the X-Fi would suit you better. Check out this short discussion on EAX vs DD:
http://forums.whirlpool.net.au/forum-replies-archive.cfm/615789.html
In terms of overall audio
quality, I'd say the Azurentech cards have it. You wont be able to notice this unless any difference, however, unless you have the highend amp and speakers that can realize that level of detail.
Like I mentioned above I also have a pro-audio interface, and I still think the X-Fi sounds really nice.
The Azurentech cards also have better digital I/O - but this will only matter to you if, like mentioned above, you have an amp/receiver with digital connectivity.
For pure gaming, especially with headphones, I'd choose the X-Fi. Creative has the gaming audio card market pretty much cornered by keeping EAX 5.0 exclusive.
If you have your PC hooked up to a high end surround sound system and are planning to play a few games here and there but mainly watch movies and listen to music, go with the Azurentech.
The
best option, IMO, would be to pick up both because then you get everything. That is a bit of overkill however