Hey i have a E6750 that i think is bottlenecking my Ati 4890 i was wondering what would be the best cpu to upgrade from it from core 2 quad range or core 2 duo.
Just add a cooler to your E6750 and a simple overclock should boost it to over 3.2 GHz. If you want quad core power go with the Q9400 at least or the Q9550.
+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.
I agree with fortunex, "E8400 or E8500 + a good CPU cooler." 45nm vs 65nm, big OC and overall performance difference. The E6750 is not the best chip for OCing.
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.