Guys, the power supply to cards is not the limiting factor of their performance in almost all cases with the 750s. You will run in to stability issues first, judging by most peoples' experience. You would also have to mod the BIOS to raise TDP. Remember that for a lot of people the cost of power will end up offsetting any tiny gain you get. Look at cryptomining blog and elsewhere, they have tested this. You are better off getting something like a palit dual x which doesn't have the 6pin and performs better clock wise than almost any other card, even at stock.
you can't rise the power limit with msi?
I've got a 750ti OC edition and a 660ti power edition. I can raise the power limit to 114% on the 660, but the 750 caps at 100% The voltage can be bumped up a bit, but of course that's different.