From what I hear the Reserator 1 V2 can radiate ~110W of heat. ... Reserator 1 V2 * 2 = 420W
Something's fishy here...
I can't find any data about the cooling capacity, whether it's 110W or 210W. But it also depends on how high water temperature you accept and how much above room temperature that is.
i7 CPU = 140W TDP
GTX 295 = 289W
Total = 429W
I wouldn't expect the water cooling to have to handle that much power. Especially the graphics can be expected to dissipate some heat to the surroundings, and not just to the water. That holds even more true if you use a water block that only cover the GPUs.
Two Reserators should provide sufficient cooling though. The question is how to hook them up, since the GPUs can handle considerably higher temps than the CPU.
With all components mounted into a single loop you will get good load balance and a smooth temperature curve.
With separate loops for graphics and CPU you will reach higher maximum temperature for the graphics but keep the CPU cooler.