I think I'll stir this up a bit with this question...
If one pump and one loop (basically) in your systems works okay... what if you put TWO loops and join them at a reservior with two different pumps one for the radiator loop and one for the cooling loop (CPU block, GPU block, HD block, etc.)?
Would a differential in flow rates of the two loops to compensate for the different surface areas in each set of thermal transfer devices increase performance?