You could even get away with a smaller PSU and still do what you want to... just be aware that you cannot do 2x580's unless you have 800W or more (technically 750W... but not with an OC), so I would do that or go a little bigger if I were you.
OCZ, while not historically known for making good PSUs, is now actually one of the best... kinda weird, but they have been doing well for themselves lately.