I wish more companies would released decent boards with an on-board Creative Labs audio chip-sets. About two weeks I go I was looking for an decent new motherboard to upgrade my home theater PC. I was specifically looking for an enthusiast level board with a creative labs 7.1 audio chipset to make best possible use of my home theater sound system. Unfortunately I just couldn't find anything. I ended up going with a Sabertooth 990FX from Asus' Tuf series. The 7.1 realtek chipset will do well enough but I really would have been happier with something higher end for audio.
I'm assuming that as a home theater PC you are hooking it up with either HDMI or optical out to a receiver, in which case a sound card (or even on board audio) does nothing. A digital signal bypasses any internal processing and is passed through to your receiver where all decode/processing takes place. Sound cards only process the signal when using their analog outputs, so people using headphones or powered speakers that plug into the 1/8th inch jacks make use of them. I just wanted to let you know, I'd hate to see someone spend good money on a soundcard when it would yield zero difference compared to an onboard optical output or HDMI out of your video card.