Well, I went for overkill. I still have a 17" Viewsonic A71f CRT and game at 1280 x 1024. It will be anywhere between 2 weeks to a month before I can upgrade to a 20" Viewsonic LCD with 1650 x 1200.
I have a 3870x2 "out for delivery" today and when the AMD 690v motherboard arrives tomorrow, I'll transfer my CPU from the outdated Nvidia 405 board. Then I'll see what fps I get in The Witcher! It replaces a 7600gs!
I agree with Lunyone who recommended you get the best you can afford. In fact, going quad core almost obligates a great card. Admittedly, R700 will be out in 6th months or so, plus 45nm quad cores from Intel and AMD, but waiting is never fun.
I do wish there were a decent chart listing the CPU where bottlenecks vanish with each card at resolutions of 1280 x 1024 and lower. One of the reasons I want to go to a higher resolution monitor when I can is to avoid any possible bottlenecks with an Athlon X2 4600+.
I want a Phenom, but I'm waiting till 45nm. Does anyone think that an X2 4600+ is too light for gaming this year? IMHO, even when the B3 stepping arrives, 65nm's days are numbered in month's, not the indefinite future.
Even if you had a dual core, CPU bottlenecking disappears at 1440 x 900, so you'd not have those issues. Getting a quad core was a good idea. For an Intel CPU, your only other choice would be waiting. Were it not for B2 errata and heat issues, I would not wait on the AMD side.