That's the same build I'll be upgrading to fairly soon. Works case scenario I can't see it pushing more than 600w.
I'd also agree with lowering the ram to 8Gb. It took me a few tries to max out my 8Gb with several instances of video editing and 3DSMax running simultaneously. I really can't see maxing it out in a practical sense happening for at least another 5 years... With obvious exceptions.