You will probably need to get a new PSU too. My RaidMax PSU that came with my case was not able to run my AMD 64 3200+. You will need one with at least 20A on the 12V rail.
AMD 64 3200+, Asus K8N-E Deluxe Mobo, Evga GeForce 6800 Video Card
1 GB Cosair Value Select RAM, 250 GB Seagate Baracuda HD
RaidMax Scorpio 668 Case w/ Aspire 520W PSU
Windows XP Home Edition SP2