I have a very similar system and a HD 5770
I run the 3DMark06 on default settings and I get 16,000
My processor+gfx are both OC'ed
When I set the 3dmark06 settings to max I got a score of ~9800ish
Just compared my RAM with yours, I have 4GB but its 1066MHz, I think..I'm not very good with RAM, but I know my mobo isnt the best and my ram is up to speed.
Other than that theres nothing terribly wrong with your rating there.