whooleo :
I beg to deffer most games aren't multi-threaded enough to take advantage of more than two cores, so the E8400 with superior IPC and overclocking ability (4+GHz I've heard) make it a better gaming CPU in 80-90% of games.
And I beg to differ as somebody who used an E6600 until about four months ago. You get a lot of stuttering with the old dual cores that just isn't present with quads.
My E6600 was clocked at 3.5 GHz. Nothing was smooth except older games. Got great frames in Crysis 2 with high res textures and DX11 using my 6950, but every several seconds the game would stutter.
Replaced the E6600 with an X3210 and the stuttering stopped immediately. The X3210 was clocked at only 3.2 GHz. Also tried it at the X3210's default 2.13 GHz clock, and it was
still smoother than my E6600 @ 3.5 GHz.
Same story in every new game I played. Get roughly the same framerate with the dual core, but it stutters. Skyrim, SWTOR, Crysis 2, BF3, all of them stuttered.