About the PSU, yeah, 1000W is too much even for two GPU's. What matters is that the +12V rail has enough amperage for the GPU. A 750W 80 Plus quality PSU should be better than a cheap/old 1000W PSU.
It's funny because the PSU I had to replace years ago was also 1000W and it didn't have the amperage required for my new GPU back then. When I bought the computer I thought "1000W that must be great", but having a quality PSU is more important than power itself.