Recomended PSU for my sistem

Hey guys i want to know what reccomended  PSU and i want to overclock my CPU to 4.2 Ghz 

Here's my setup:

CPU: intel core i5 3570k

GPU: Sapphire Radeon 7950 3GB

RAM: 8GB 1666Mhz (sorry i don't remember it's Mhz count it's around the value i just written)

Motherboard: MSI z77a-g41 8 pin needed to power my cpu

If you guys help me choose i really apreciate it

XFX 550W bronze +

Corsair CX500M

What PSU have you got already running as it might be fine?

To be honest i don't know my friend's PC CPU fried and since he doesn't know how to dismount a PC i asked for it and it was a 400W from 2005 and its a big crap

And yes it only said in the sticker it was 400W nothing more

Budget?

Corair,XFX,Seasonic.

Pretty much anything from those manufacturers, choose wattage and if its modular or not to suit your own needs. 500W-600W seems to be the ballpark.