While sometimes it is more economical to have multiple rigs running (for power and cooling reasons), I am limited by the number of systems I can operate in the house. Having said that I would like to know if there is any way to power 4 unlocked (880MHz or OC 900Mhz) 6990s out of two Thermaltake 1200W PSUs (model number W0133RU). I have a case which supports dual PSUs (TJ07), and the ATX adapter cable which turns on the second PSU when I switch on the power.

Here is the problem. While 2400W combined "should" be enough for practically anything, I would like to know if I would be overloading the 12v ATX rail (4 GPUs + Phenom II X6 1090T/890 chipset. There is no way to "glue" the power of two ATX rails. I know that the CPU rail is there to help out, but I don't know if it will be enough.

I will invest in external watercooling to keep things running smoothly, so heat will not be an issue, and the cooling won't burden the PSUs.

Any thoughts?