Im using AMD64 3000. Nothing special. This is due to the lack of 64BIT programs. However you get nforce 3 which gives you unreal memory scores in benchmarking programs.
Chat to the guys at www.planetmars.co.za they are quite clued up on CPU's etc. Also the following link might be of interest: http://www.silentpcreview.com/article169-page1.html