Looks like it has a single 45A 12V rail, that is pretty weak for a supposed 750W unit. What else are you running in the system? A GTX 260 uses about 180W, so with two of them you are using up 360W from the 12V rail and your PSU only has 540W available so that only leaves 180W for the rest of the system which is a little tight, and with a 12V rail that weak i doubt the ultra can stand being run at full load so i dont recommend it. I suggest you look into a good 750W unit, like a Corsair 750TX, Antec TP-750, or an XFX 750w. They are all much more powerful than your 750W unit as they all have ~60A between their 12V rails.