You have a core2quad, which is hurting your score. Overclock it, as mentioned above, and see your score climb. Also, WHY are you using 3Dmark06? Get Vantage, it is DX10 and is much friendlier to the newer hardware. I get about 26,000 in 3dmark06 and it is all because of my 4GHz i7. If I put your card in my system, I'd probably get about 28-30K. Your score is fine, it won't reflect in your game play.
Besides, do you really sit around and run 3dmark all the time to get your jollies? It's a benchmark tool and that is it. Are your Frames hurting in games?