Hi there,
I don't actually use the on-board sound chip on my PC and, to be honest, I haven't since my very first computer. I have always found these chips to be lacking in one area or another.
However, saying that and having looked at the Realtek site (
http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PFid=28&Level=5&Conn=4&ProdID=173 ) I think your sound should be better than you are currently experiencing. According to this page the following are available:
HDMI audio driver for AMD platform
Dolby® PCEE program™ (optional software feature)
DTS® CONNECT™ (optional software feature)
SRS® TrueSurround HD (optional software feature)
But it does say they are optional software features so it could just be a configuration setting that you need to make but, to be honest, I'm not sure where that would be made.