So perhaps a little misunderstanding, but giving the initial poster advice about RAM as bottleneck is misleading, too!
Gain fps with videocard and its vram. Secind step, when still having problems: upgrade cpu and ram, but cpu should in this case have less influence, although another, faster clocked cpu with ddr3 ram is apprecuated , too. I do not exactly know, if the quad and its ddr2 in his case could also be a bottleneck afterwards....
As I have an old i7, I am currently not running in any priblems and the 2 fps more with a new generation is too expensive for me, because the watercooling also costs some money. First of all I will switch to eyefinity with 3 monitors. Later, the cpu will be substituted.