You can hook up any sound card up to your home theater receiver. You can always hook up L/R RCA audio cables and you can get up to Pro-Logic sound.
The real question is if your receiver has digital inputs and what ones (coaxial or optical)? Then you just need a sound card that supports that output and you can get the better 5.1 or 6.1 sound. I only use a SB Live! value myself and it hooks up for Pro-Logic sound, but it still sounds great on my good speakers. I bet it sounds better than any computer speakers you can buy, but of course the speakers cost me close to $1,000 and good computer speakers are a little cheaper than that.
One of these days I will be able to afford really good home theater speakers, but my wife insists that the ones we have are good enough. Maybe when I start making a 6 figure salary she will decide otherwise. One can always hope