Do they have an OS?
Who cares? http://www.cyberpowerpc.com/system/Gamer_Ultra_7000_Elite
Get this. And instead of using the crossfire 6450, just use the apu's integrated. It'll easily run mine craft at 1080p over 60 fps maxed out.
Downgrade the liquid cooling also, and change your motherboard to the one that is -22 money, you won't need the extra features. You will hit $600.