Most definitely. I mean We're getting alot of CPU orientated games, HL2, Crysis, etc.
I had a Athlon 5000+ Edition OCed to 3.4 and it ran well (ofc at the time well meant 30-40 Frames). After that I changed to a Q6600 Quad core CPU and OCed it to 3.24 and I got alot higher frames.
I was up in the 50 and the game itself, even though the frames were the same number in some case, felt alot smoother.
I also noticed a difference when my gf played sims 2, when she moved around in the neighborhood, it was alot smoother.
So yes it would limit it, but not by an HUGE amount