UnOfficial Asus Rampage II Extreme Thread

[overclock]

Hi all,
I have been using the included X-Fi riser card that comes with the RE-II. Now that I have loaded the comercial version of Win 7 I am actually going to put this rig to work. I want to upgrade the sound card. In the opinion of this august group what is the best sound card for this Mobo considering in the following order:
1. Quality of sound
2. Being able to fit
3. Compatability with the RE-II and Win 7
I am looking for the best, not the cheapest.

I am looking at the ASUS Xonar series, anyone have any experience with them?

I own a Xonar DX with the Rampage Extreme 2 plus 2 Bose loudspeakers and a Technics amplifier. The sound quality is far better than the sound card provided with the Rampage, especially on music and games.