I'll join my fellows and recommend the Sandybridge. The new architechture of the Intel CPU has killed even the old Bloomfield, not to mention the AMD. If you want to wait for the AMD Bulldozer you may, but it has yet to be seen if the Buldozer can topple the Sandybridge.
As others have stated right now the 2nd generation Intel® Core™ i5-2500K is about the best gaming processors on the market right now. If you are going to higher end work like video/audio or some other heavily multi-threaded application you are going to want to use the Intel Core i7-2600K. These processors are unlocked giving you the ability to reach even much higher speeds.
You understand that overclocking of the Intel® Core™ i5-2500K isn’t based off from faster memory? On the Intel Core i5-2500K we have unlocked the multiplier on the processor allow you to overclock the processor without changing memory speed at all. Because of this change to overclocking of the Intel Core i5-2500K there is very little real value in memory over DDR3 1600.
I know but I like big numbers you see plus I like to make my PCs last a good few years. The PC I'm on now has served me well for about 6 and to be honest, I could probably squeeze 2 more out of it but an upgrade would be better and is long overdue
I went with:
Asus P8Z68-V PRO Intel Z68
Intel Core i5-2500K 3.30GHz possibly with a Coolermaster V8
Corsair Vengeance 8GB (2x4GB) DDR3 PC3-12800C8 1600MHz 1.5v
With 2 crucial M4s in RAID 0, it should be reasonably quick and I was thinking of waiting until BF3 comes out before buying a new graphics card.