Originally Posted by xHawky
*ASUS Xonar D2X
*ASUS Xonar DS
Which would best meet my needs?
Discount the Xonar DS entirely, due to lack of headphone virtualisation.
The Xonar D2X would do the job and comes with the multichannel version of PowerDVD bundled. EAX support isn't quite as good as the X-Fis though. If you already have a 5.1 version of PowerDVD, you could get the Xonar D1 or DX. They have headphone virtualisation and are cheaper.
I dont' think either X-Fi card decodes Dolby Digital and don't include DVD software. If you have some 5.1 DVD software they'll be OK. They're somewhat better for gaming, but I prefer Dolby Headphone on Xonar to CMSS-3D on X-Fi. You may find that CMSS-3D has better synergy with HD555s though.
Unless you're very fussy about gaming audio, I say Xonar D2X (or D1/DX if you don't need the bundled software).