Go with an Intel processor. Like a Core2 Quad or maybe a 2.6 GHz i7.
(Speed does not matter as much as everybody thinks, it really is the generation and the cores. The Core2 Quad has one that is 2.83 GHz, whereas the one of the i7's is a 2.6 GHz, but performs better.)
Everything else looks good.
EDIT: You'll have to change your motherboard too.