nolarrow, yes.
I got mine to fix the lack of shielding with interefence/ motherboard noise which started to really bothered me. Listening to webpages load up via squeaks from the speaks was awful. A better motherboard would have cost more and I just wanted to spend money and a soundcard was that next thing.
They don't cost that much and my Xonar is way better than the on the motherboard sound.
The difference between the HDMI bypassing the soundcard and then hooking it back in is noticeable for games and it really makes films better.
Also, my large headphones need a bit more power to drive them an the output from the motherboard doesn't cut it. The sound card is able to. In an ideal world I'd have an AMP to drive them. They far too much.
After you go back to a dedicated card to realise just how bad the motherboard options really are.