halodude23 :
Thank you for such a thorough answer, you said that there wouldn't be any more room for overclocking, but what if my GPU loads are up to 100% both +the CPU Usage? Would that complicate the PSU itself?
The biggest problem with the OCZ ModXStream Pro Series 600W (OCZ600MXSP) is its +12V rail distribution.
+12V rail distribution, each rail is current limted to a maximum of 25 Amps and a combined maximum of 42 Amps:
+12V1: The cables that are permanently attached to the power supply (i.e. ATX 20+4 pin connector, 4-pin ATX 12V connector, 8-pin EPS12V connector)
+12V2: The cables from the modular cabling system (i.e. PCIe supplementary power connectors, SATA power connectors, 4-pin Molex peripheral power connectors, FDD power connector)
Having both graphics cards obtaining all of their power from the +12V2 rail under a full gaming load will mean that the graphics cards alone will be drawing almost 20 Amps leaving just 5 Amps to power the SSD, HDD, CPU cooling fan and case fans. If the current draw on this rail exceeds the maximum 25 Amps allowed the OCP (Over Current Protection) circuit should kick in to prevent the power supply from burning out.
The CPU is being powered from the +12V1 rail.
I would be considering a good 750 Watt power supply if I were you. At least it would have at least four PCIe supplementary power connectors and enough spare capacity for overclocking both the CPU and GPUs.