Stick with a receiver. Any halfway decent recently made HT receiver has lots of decoding options including DTS HD Master and Dolby TrueHD for Blu-rays, and typically a variety of Dolby Pro Logic II and even stereo upmix (sim surround like Dolby Neo) options for gaming. You can end up with digital or analog sound whether you have a sound card or receiver though. It varies from brand, model and type of receiver, card or speakers you get.
Furthermore you don't have to worry about poor driver support, which is common with sound cards. All sound cards are at the mercy of whomever manufacturers the main chip for them, or DSP. In many cases people will try and use drivers from another brand card when the card manufacturer doesn't keep up on drivers well.
A receiver will also have huge slit foil caps, vs small slit foil or all solid state caps on a sound card. Solid state caps are being used a lot more on sound cards now because they run cooler and last longer, but it's largely due to sound cards having a rather small PCB, in which case extra heat can get transferred to them from the DSP chip. Conversely, receivers have the space for huge heatsinks and separate PCBs for amp and DSP , so they can run big slit foil caps no problem.
Slit foil caps give you more warmth in the midrange and bass. They have a more anaolog, less digital sound vs solid state caps. I chose a Yamaha receiver because they use a DSP that is designed to sound more natural and less digital. Because of this they are pretty good for playing music if you prefer an analog sound.
Honestly, when you consider MS has dropped HAL (Hardware Audio Layering) support ever since Vista, sound cards don't make much sense anymore. Because of it surround sound in games when using a sound card is hit and miss, and is always software vs hardware driven anymore. Even Creative cards need their Alchemy software to support surround sound.
There's also the fact that the HT receiver market is WAY bigger than the sound card market, so you can commonly get $300 receivers for $150, about what a decent sound card goes for. Even the HT speaker market is much bigger than the PC speaker market, so you can get better deals there too. Just don't assume you have to get the little HTiB speakers to get a good price.
I just picked up some Jamo HT speakers with floor standing fronts and a Jamo 8" sub for only $250 at Fry's. My movies and games have never sounded so good. If you ever make it down to the Dallas area, Fry's have
these for $200 (I got mine on sale for $150). They also have
this for $150, but will match Vann's price. Even at $400 total, this sub & speaker set is well worth it. Jamo is made in Denmark and now owned by Klipsch, whom put a 5 yr warranty on them. They use butyl rubber surrounds on the drivers and real hardwood veneer on the MDF cabinets.
I was considering Denon or Pioneer on receivers. Denon tends to be very clean sounding with discrete amplification for each channel. Lower in actual watts power channel, but you don't have to turn them up as much. Pioneer is about the same as Yamaha as far as amp clarity and efficiency, but has a more neutral DSP. Denon's DSP tends to sound more digital. Both actually sound more digital than Yamaha, because the fact is, you really need a DSP that tries to impart a natural analog sound to get away from the digital sound of most source material in movies and games anymore, which is what Yamaha's DSP is designed to do.
So, basically if you think you want a fuller, more analog sound, you may want to listen to some other receivers and speakers, esp if you have the tiny HTiB speakers. The mids in those sets commonly don't play low enough to match what the sub can do, so you don't get full range sound. That in itself can make everything sound more digital, along with hard vs soft dome tweeters, the latter of which Jamo uses.