If you can get a good HDMI capable receiver and good audio system, then screw the sound card.
Or you can get a good amp and just go analogue out with a high end sound card.
Your choice really.
Or you go "audiophile" grade and get everything. Get the whole ASUS package which includes GPU and audio card and wire them up, will not go into details as you can easily read about it on ASUS's website, shoot your audio and video through the HDMI to high end receivers and into your HD-HIFI HTC setup.