core 2 quads are still on par with amds latest offerings for gaming performance but the newer intels do lead the way.
yes a faster cpu will get more out of the card but gaming performance is still more about gpu power than that of the cpu that feeds it.
you could argue that your hdd or ram is also a "bottleneck" as the latest ssd and ddr3 @2.5ghz are faster and yeilds more performance too, but thats the case for everybody.
yes faster kit will open other parts up more but is that extra % of performance worth the cost to you?
i have a c2q, amd x4 and a 25k here and tbh the only time i know the difference is when i look at benchmark scores. well and when i try and warm my feet on the air coming out as sandy is a cool running chip and crap as a heater :|
gaming wise i imagine i get better min fps but it is still the same gpu that its feeding and it has the final say on my fps.
if i was you i would buy the gpu and better cooling and see how high you can get your fsb