I'm not as much of a gamer as I used to be. The most recent games I have played are Half Life 2, Battlefield 2 and Battlefield 2142. BF 2 > BF 2142.
Gigabyte GA-P35C-DS3R (Core 2 Quad and DDR3 compatible for future upgrades)
Thermaltake 700w PSU (I don't overclock)
... plus peripherals.
I'm hoping this gives me decent FPS at the above-listed games. I'm movin up from a P4 2.4, 2GB DDR 266, (2) 80GB UATA133 HDs in RAID-0, ATI Radeon 9600 Pro. That setup was decent on lower settings.
After viewing the test results, it looks like the AMD has floating point calc advantage over C2D (almost double), but the C2D > AMD in everything else.