+1 to Dirtmountain
Just buy a better cooler and overclock it and you will not have any problems with bottlenecking. My only concern is the motherboard but it should be able to support at least a bit of OC.
If you want to be sure that your video card will not be bottlenecked by the processor , you can OC to 3,2 Ghz (FSB 1600) and you will be more than fine. So I don't think you should spend any money except a better cooler (if you don't have one already).
I currently have a E6750 overclocked with a simple Arctic Freezer 7 Pro cooler that is under $30 to 3.4ghz. You should also consider a motherboard upgrade before a processor upgrade. I would recommend a crossfire Gigabyte board with the P45 chipset ($135). If you really want to go quad then go with the Q9550 ($220) and overclock it. The huge cache of this processor is what is going to help your gaming performance. I hope this helps.