For the processor you may want to consider a Phenom II x2 and a motherboard that allows you to unlock the other cores. From what I've read the odds of getting a functional quad core out of it is very high.
don't buy a X2 hoping to get a x4 out of it. i can attest that the chances are still a matter of luck and there is no sure thing. If you want a quad core, buy one. If you can live with a dual core, get a x2 and hope for the best.