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.
and i just found a 725w psu and if i couple that with my old 500w psu would that work?No, it would likely not, and I would strongly advise against it for safety reasons. PSUs that are not specifically designed to operate in parallel may cause issues as one sources more current than another due to minute variations in voltage. However, if you downclock even more you may be able to get the consumption under 725w although whether that's reliably doable is not something I'm sure of.
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