Get a Soundblaster X-fi ( Fatality) and you will be much happier, put it in the PCI express slot and install the Software, forget about the onboard sound. Realtek gives a lot of trouble with the rear speakers. It's notorious for that. There is in the software of the Soundblaster a way to set the speakers as you want them. And the sound is way deeper, bigger and better. You will be asking yourself why did you not do that in the first place. I mean I did. I thought the onboard sound was reasonable, but it is bad compared to a good Creative Soundblaster, Asus Sonar or even an Auzentech.
Just go for it. You won't look back. Expect your ears to having a treat.
KJ