Scores would be a lot higher with a quad core. The E8400 helps but it's still just a dual core. Also, for the 3DMark06 calculation, the CPU score is halved so it doesn't have quite as much of a contribution. If I get bored one day I'll be tempted to crank the E8400 up to 4.5 and see if I can break 13k... I don't think it'd be enough though.
Anyways, this thing's running games really well. If you were running a really high res, other cards would be better, but I'm just running at 1400x1050 so this does the trick.