You have a 350$ audio system and were using the onboard audio !? It's probably the best computer speaker system on the market right now. If I were you, I'd get the best sound card possible pronto !
You could have a look at the Asus Xonar Xense
. It's in my opinion the best deal you can have out there. You have a 200$ value sound card and a 200$ value headset for 280$ (you also get free shipping).
If that's really too high for you, take a look at the Creative Labs Sound Blaster Titanium Fatal1ty Champion
. It's the second best.
In third place, you've got the Creative Labs Sound Blaster Titanium Fatal1ty Professionnal
Finally, the Creative 30SB088200000
is not bad either.
Hope this helped,