I think some people really underestimate the need for CPU power in modern games. An A64 X2 at <3GHz or a Phenom at 2.5-2.6GHz (as would be expected out of a 9600) is not enough to play a game like Crysis when paired with a high-end video card.
I have a GTX 280 @ 712/1458/2520 and my previous CPU was a Phenom 9500 @ 2.5GHz and my new CPU is an E8400 @ 4.0GHz.
I ran some tests with the Crysis "Assault Harbor" benchmarks with both systems. Note that there are two minor differences other than the CPU; the E8400 is running on Vista 64-bit and I had the Phenom 9500 running on Vista 32-bit, and with the new E8400 system I am using the 177.41 drivers, versus 177.39 for the Phenom system. I can't see either of these factors making a huge difference. The E8400 tests were run with 32-bit forced. The TLB patch was disabled on the Phenom system.
Assault Harbor, 1680x1050 DX9 High No AA
E8400 @ 4.0GHz : 53.0 FPS Avg, 36.3 FPS Min
Phenom 9500 @ 2.5GHz: 31.9 FPS Avg, 17.0 FPS Min
E8400 > Phenom 9500 = +66.1% Avg / +113.5% Min
Assault Harbor, 1680x1050 DX10 VeryHigh No AA
E8400 @ 4.0GHz : 29.3 FPS Avg, 20.2 FPS Min
Phenom 9500 @ 2.5GHz: 23.3 FPS Avg, 12.9 FPS Min
E8400 > Phenom 9500 = +25.8% Avg, +56.6% Min
Honestly I'm surprised at how big the difference is myself, so I'll have to see how the game performs with E8400 @ 2.0-2.5GHz or so just to eliminate any non-CPU differences between the systems. But there is no doubt that CPU plays a big role in Crysis at least, and remember that the Assault Harbor level is actual gameplay, not a flyby, so it will accurately reflect what you will see while playing Crysis. The biggest difference is in Min framerates and that clearly impacts playability. I haven't played Crysis much yet with either system (already played it several times previously) but from playing the game @ DX10 VH, it is perfectly smooth when IMO DX9 High was not 100% smooth on the Phenom / GTX 280 system.
Anyway.... I just wanted to show that the CPU is not worthless when it comes to gaming, it does make a difference. I'd highly recommend you go the Intel route.... there is no comparison in performance. My E8400 is faster in everything, including rendering (Cinebench), gaming, 3D Mark, everything I do, compared to the Phenom 9500. In fact considering I can now run 64-bit Vista (B2 Phenoms OC like crap in 64-bit Vista for some reason) I am getting ~15-20% higher Cinebench scores than with the quad-core Phenom. And my single-CPU is score is more than 2x the Phenom's.
EDIT:
I ran a DX9 High test with the E8400 @ 2.33GHz and got:
-40.1 FPS Avg, 15.3 FPS Min
vs. 53.0 FPS Avg, 36.3 FPS Min @ 4.0GHz