I would emphasize that CPU speed really doesn't matter. My main mining rig is running an Athlon X2 4200 @ 1ghz to save on power.

Also that the most important thing with power supplies is the amount of wattage/amperage available on the 12v rail(s). Do not just simply look at the overall power (ex: 600watts) written on the front of the box. I have a 400w Enermax that puts out more 12v power then some 700w PSU's i've seen on Newegg.