Will a 750w PSU run this setup?

you should be okay...i have seen where custom builders are using the corsair tx 750 with a gtx 285, crossfire-4850, cross-fire 4870....the crossfire rigs will sap more juice than your system ....i would not worry about it...and good luck with your build. looks like a great rig. if you have the extra $, go with the hx 750...better components under the hood