I will say that onboard audio sucks simply because it uses processor time which lowers your FPS in games (albeit maybe not by much, but every little bit counts). While I don't think a $200 sound card is worth anything to most people, those most people will still notice the difference between onboard sound quality and a good $50 sound card. Not like anyone daily checks the "happenings" in the onboard sound card market, but the last good onboard sound I remember was on the nForce2 boards. Since then I don't think anything has topped that. Some boards still use the AC97 chipset.
Here's a good sound card on the Egg:
http://www.newegg.com/Product/Product.asp?Item=N82E16829111002
While not the best, it's the same card I use due to space constrictions with SLI. Before that I was using onboard sound after losing the space to use my Audigy 2 ZS. It was a dark dark time, using that onboard sound.
<Lyme> I got Fight Club for 6.98 at walmart.
<Black_Bishop> I am Jack's low price guarantee