Originally posted by: plion
Why chizow? Isn't it a console port? doesn't make sense
Yes its a console port, but like most console ports, GTA4 is far superior to the console versions provided you have the necessary hardware. In GTA4's case, the increased visual quality from higher resolutions and texture quality aren't the problem, you'll see very little difference between mid-range DX10 to high-end DX10 video cards, just a benefit from more VRAM.
The increased view distance, shadows, car density etc. is the problem as these settings all significantly increase demands on CPU time. GTA4 is also heavily threaded to take advantage of the highly parallel RISC CPUs on the consoles, which again gives slower-clocked Quads an edge over faster-clocked Duals.
PCGH GTA 4 CPU benchmark
You'll get pretty good frame rates on your rig since you have a fast C2D, but it'll still play much better on a Quad. Turning down viewing distance, shadows, car density to the absolute minimum will significantly increase performance and the game will still look better than the console versions.