DDR2 isn't available for AMD until the new socket comes out I believe. Intel uses it currently though.
If you want the absolute fastest, You are going to have to find some low timing BH-5 memory. I've seen some people run the stuff at 250-260 1.5-2-2-0 or something like that. It's hard to find, not sure where. My memory was inexpensive if you ask me, and performs better than stuff twice the price....research pays off