How much of PSU does my O.C. Gaming PC need?

[tae912]

Case: NZXT M59
Motherboard: ASUS P8Z77 V-LK
Processor: Intel Core i5 3570K IVY Bridge 3.4Hz (3.8Hz turbo)
RAM: G.Skill Ripjaw X series 8Gb DDR3 1333
Video Card: EVGA Nvidia Geforce GTX 670 2GB
CPU Cooler: Corsair Hydro H100
Fan: 3 Xigmatex blue led crystal series
OS: Windows 7 Home Premium 64-bit
Current PSU choice: PC Power and Cooling Silencer MK II 750W High-P. 80 Plus Silver.

Those are my current budget build planned and my PC, again, is going to be for gaming purpose.
I'm not too familiar with O.C. (planning to learn it after i purchase all of these) but im planning to do that in the future.
With that being said, i don't know how much power supply i would need for it
i heard 4.0 or 4.2Hz is a safe area to stay O.C. so thats what i am planning to aim for.
do i need more than 750W psu?
If you do know, what is my build capable of?

hoping for this computer to play BF3 ultra setting at 40+ fps at least
thanks for reading guys and hope to hear from you soon!

 

[nafoni]

If you want to SLI in the future, stick with that 750W. If not, a 650W should be more than fine.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139020&nm_mc=AFC-C8Junction&cm_mmc=AFC-C8Junction-_-na-_-na-_-na&AID=10446076&PID=3938566&SID=

Oh, and you'll get more than 40 FPS in BF3 @ ultra @ 1080p. Probably more like 60-70.