750w is already overkill unless you are going to be running two cards at once. How many watts you actually need depends on what card you get and that really depends on what you want to spend. If you can afford it this is a great deal and comes with 3 free(and actually good) games;http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.455049
A 500w PSU of a good brand(Corsair, Antec, Seasonic, ect.) should handle the card just fine.