Original Fuzion GPU or the V2 block? The first is pretty brutally restrictive, actually, while the second is only half as restrictive.
The CPX-Pro is better than a lot of people give it credit for, actually. Plugging in a few numbers in Martin's flowrate estimator, you should be okay, even with the GPU block. But the second radiator might be worth considering, especially if you use the rig for folding.
__________________ i7 2600K | ASUS Maximus IV GENE-Z | GTX Titan | Corsair DDR3-2133 |