I'm not sure but I think most people tend to really tone down graphics quality to gain a higher score. I hit 12,400 with my 9800GTX + C2D E6600@3GHz with quality turned way down. It drops by 1k I think with normal quality. Another big factor is the CPU. 3GHz is good but higher will net you more performance than you think!
nVidia cards are better at 3dmark than ATI. That is true.
There is nothing wrong with your system. 3dmark is an ep33n benchmark that actually tells you hardly anything about your system. You just built a really nice system, stop worrying about stuff that doesn't matter and enjoy it.
If you really want to see how it stacks up, benchmark it on Crysis 1920x1080 Very High Quality with some AA/AF turned on. If its playable, you win.