A motherboard isn't a component which draws power as so to speak, rather co-ordinates hardware across circuitry which require power. The Motherboard wont be a factor rather the GPU/CPU the main ones, which 750W is plenty of headroom for that given it's a quality power supply unit. Yes the motherboard takes in the power for the CPU, and supplies 75W out of the slots for GPU's, but that is not for the Motherboard.