Don't get an X2. Get an Opteron 165 Denmark. They're much better at overclocking on near stock voltages and stock cooling. If you have to get an X2 get either a 3800 or a 4400. Reason being, the 3800 and the 4200 both have a 512K cache and are pretty much identical, the only difference is the X24200 is 200MHz faster, nothing that can't be made up with a simple overclock. The 4400 is 200MHz faster than the 3800 aswell but each core has a 1MB cache.