The problem, though, is bass management.
Any "computer" sat/sub system will have a simple analog crossover in the sub, optimized for the satellites and the subwoofer in the system. All the computer does is generate 2, 4, or 5 channels of sound, and the speaker system decides which frequencies go to the sats, which frequencies go to the sub, and how to blend the meeting point of the two.
On the other hand, an HT receiver DOES NOT do that. An HT receiver does A LOT of things that computer speakers don't do, but, in the name of "signal purity" it simply takes the 5.1 / 6.1 / 7.1 inputs and amplifies them. In that sense, you don't even need an HT receiver, all you need is a cheapie multichannel amp for the speakers.
Now, here's a problem: Any speaker than can reproduce frequencies below 100hz with any degree of aplomb will NOT fit on your computer desk. Any speaker that can reproduce frequencies below 60hz or so belongs on your floor. And an appropriate center channel will crush your puny LCD or even a CRT monitor (while looking perfectly at home perched on top of a big-screen TV)
Your choices: Outlaw Audio ICBM (all-analog bass management system, about $250 list) or doing bass management on the soundcard level.
The problem with doing it on the soundcard level is simple - no soundcard does bass management, gaming, and music well enough to do justice to an HT setup.
The Audigy2ZS, when toldd to do bass management, will forcibly convert your 44.1khz sampling rate music to 48khz, introducing audible artifacts.
Via Envy-based soundcards cannot do 3D audio in hardware (making them glorified Realtek soft-audio chips for the purposes of gaming) and, thus, force your expensive CPU to spend its time computing 3D sound effects instead of computing physics, AI, or something that CAN'T be offloaded to a peripheral chip.
Older soundcards do not have flexible enough bass management.
I was researching HT on the desktop, but came away with the impression that the size of the equipment, the pricing, and the capabilities do not match what I need in PC gaming. I ended up getting a set of Klipsch Promedia Ultras for $277 shipped from Dell, after taxes, and have been enjoying the set ever since.
For something a little more expensive, and a little more "musical" sounding, consider Creative Labs Gigaworks S700 (5.1) or S750 (7.1) system. For better flexibility with movies, the Logitech Z5500 is almost a tiny receiver in and of itself, with DD and DTS decoders built in.