That configuration should work (the connectors are correct 6-pin PCIe auxiliary power connectors that appear to be properly wired), but it is close to the power supply's limits. Since power consumption goes up with clock speed, I would advise downclocking a bit (it would help with cooling as well). At 1400gh/sec it should only use 800-900 watts or so according to
this post.
Would that be a better option or should i invest more to get 2 750w or something and overclock it a bit?