The Best Gaming Sound Card

Hey folks, I've been a long time reader of Toms but this is the first time I ever posted a question and please forgive if this has been discussed to death already...but,
I need to know whats the best soundcard out right now, to go with my new Astro A40? I want the best quality possible and price doesnt really matter. I've recently got into gaming on my pc and put myself together a gaming rig, which I'm 99% happy with. The only remaining issue, is audio quality. Right now I'm just using the onboard soundcard of the ASUS P6T DeluxV2 thru TOSLink to the MixAmp of the A40s. I didnt think there would be THAT big of a difference with the quality of games,music,movies until my buddy came over and said "oh cool, now you need a kick ass soundcard to go with the headset...." which gots me to thinkin. I've been searchin the net to find an answer, a soundcard or second opinion. ANYONE have any advice?? I was looking at the ASUS Xonar Essence STX.

Thanks in advance, I appreciate any advice!
SLU

"...A fool and his money are easily parted"