Well, my configuration is exactly what you are thinking about buying. --Edit: I have a 8800GTS 640, not a GT
Said that, my answer is: YES, the CPU will be a bottleneck.
In Crysis demo, at the sunrise scene (over a hill), my FPS stays locked at 19, even if I turn down the graphical detail from all High to all Medium, a strong indication that the bottleneck is the CPU.
Looking around for a replacement, I really think I will wait for the Phenoms to come out. Another possibility that I am thinking of is the Athlon 64 X2 5000+ black edition.
I will surely stay away from any 90nm processor from AMD. Mine runs hot and no overclocking possibility whatsoever. Yesterday I tried a little bit and the temperature went sky high with system reset. And I have one of these little monsters:
http://www.evercool.com.tw/products/hpc-925.htm.
My advice would be: right now, wait for new AMD CPUs, or buy Intel. Oh, I like AMDs, my only intel was a Pentium 100, but right now is not the time to buy AMD