Overtime yes, but 750W means it will be able to supply the full 750W, the efficiency means that
80% efficient
750 / .8 = 937,5
937,5W from the wall to supply the full 750W. The remaining 187,5 is turned into heat.
The 980 Ti's have a max TDP of 250, and the CPU 130, and even then. You'll likely not push the GPU's to the limit unless you stress test it using a synthethic benchmark.
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I would personally still go with a 1440 at 144 Hz monitor, or at least consider G-sync, at that budget. Or does OP already have a monitor?