COH is even one of the more cpu limiting games and even there it makes little to no difference. every single game is basically designed with an engine that uses a currentish cpu to base how much power it can use. there is no game that won't run fine on a x2 3800. the only games that "can" push that are supreme commander, but thats again generally when the game scales up hugely. with pretty normal unit counts its fine framerate wise, and thats i think the single most cpu limited game ever.
as said, any game is cpu limited at low resolutions, but a 7600gt owner shouldn't be playing at 1024x768, and a 8800gts owner shouldn't be playing at 1280x1024, and a gtx owner shouldn't be playing anything less than 1600x1200. likewise if you only have a 1280x1024 screen you SHOULD NOT buy anything more than a x1950pro, if you have a 1920x1200 screen and you want to game you shouldn't buy a 7600gt.
you have to buy a screen you are happy with and not way below/above what you want to use it for, and then buy a gfx card based on your resolution, and not what its called, who makes it or how new it is.
i could name maybe 3 games that are "slightly" cpu limited, sup commander, M$ flight sim, that other flight sim, and maybe COH, and even 2-3 of them aren't that cpu limited.
what people need to remember is, if you run at 640x480 and you can get 340fps, THAT is a framerate your cpu is capable of, when you up resolution basically there is NO extra cpu work to do, its all extra work for gpu. so if you're running at 100fps when you get up to 1920x1200 you'd are not cpu limited, you already know the cpu has enough juice to push out info fast enough to pump out 340fps.
x2 4400+ won't be pushed for a while, i highly doubt crysis will push that 4400+ much even it it was at stock. alan wake, well, if you've seen the in game vid of the tornado running, it might be pretty much the first game to actually require a dual core cpu minimum(though i'd guess you could turn off a lot of physics options and run on single core, but looks like you'd be losing a LOT), might even push a very high clocked dual core or possibly a quad core.
the Alan Wake people are saying stuff like "it supports quad core", but every new engine and game always advertises all the latest stuff it CAN use, can and need are very different. for instance source is getting a multi-thread upgrade, so i think HL2 will be able to use dual cores, but there is flat out no way in hell HL2 "needs" dual core, but it will support it.