I went ahead and got the Xonar Essence STX and it is by far the best sound quality I have ever heard on a PC.
I've had Creative X-FI Fatal1ty gamer and the Razer Barracuda AC-1, but this Asus one is by far and away the better device. I heard sounds in BC2 I have never heard before, the bass is better and the explosions kick ass! For music it's just plain fantastic as well. If anybody's looking for a really good sound card I highly recommend this one.
The only downside to this card is that it required two 3.5mm female adaptors to plug into the back of the sound card for the mic and the headset and only ships with one 3.5mm adaptor. That said, the drivers work flawlessly with Win764 and the things sounds great, way better than I ever expected for any sound card.