I think your best bet is a p5n32-sli, but the 590 chipset supposedly isn't that great of an overclocker (correct me if im wrong anyone who has a 590 chipset for C2D pls). The 4300 is a good budget proc right now but the e6320 is supposed to come out some time with 4mb L2 cache enabled. Again can someone tell me when thats supposed to come out (sry ive been out of it for a while
The 680i boards are the chipsets meant for overclocking and full x16 x16 sli for the c2d but it will put you out of your price range for sure.
Nvm about the e6320 date...according to anandtech its supposed to arrive in q2.
here is the p5n-e lord anthrax suggested: p5n-e
and here is the one i suggested: p5n32-sli