Actually for performance of your CPU, watercooling all of your other parts simply adds heat to the water that cools your processor and more heat means less performance.
Now if you wanna get more than a little wild, get a second smaller exterior mounted radiator and inline pump on a slightly small diameter line and watercool all your other parts separately then I say go for it.
But I think for GP I would simply isolate my power supply a little better. Make the power supply isulated to the interior with its own air duct intake that draws from outside the case with the exhaust louvered up and away.
And aren't those Koolance cases?
Koolance