If you're running rated power (750) at 2 ohms and a short distance 12 awg would be adequate.
But If you're running at 1 ohm it would drop you to 8 "ideally".
Also keep in mind -- the power rating of your amp is rarely, if ever what the sub will actually, so a size smaller would not cause any problems. You'd have no losses with 10 awg at 1 ohm.