What PSU I should buy?

I'd say anywhere from 500 watts to 600 watts would be more than enough. In truth, you need to pay more attention to the amps on the 12 v rail (s). You want at least 30 amps on a combined 12v rail (with everything else). State your budget and we can help you find a suitable power supply. Also state your country (to determine website).

Thanks for the fast response.

Country - UK
Budget - £100-150ish

no need for something like this then?
http://www.dabs.com/products/ocz-technology-1000w-max-p...

Thanks once again.

No need for a 1000w watt power supply for that build.

Something like this will do just fine.. http://www.overclockers.co.uk/showproduct.php?prodid=CA...

Moley

1000w maybe if you overclocked your cpu to 5.5Ghz and had 2 670's overclocked to the max even then you would be using about 800w,850w at max

http://www.dabs.com/products/corsair-750w-gold-professi...

http://www.dabs.com/products/antec-750w-high-current-pr...
2 good ones.
-Bruce

Absolutely no need for that - fox is correct, a quality 550w
unit is plenty, no harm in going a little more than that, but
it isn't necessary.

Quality brands: Seasonic, XFX, PC p&cooling, Antec, most Corsair's, Enermax
and a few others. And you could do very well at the lower end of your
budget amount.

Tom

http://www.dabs.com/products/antec-ea-550-platinum-8284...

http://www.dabs.com/products/xfx-650w-xxx-edition-semi-...

http://www.dabs.com/products/corsair-650w-gold-professi...

OCZs are not so great PSUs.

Seasonic M12II-620 £74.34

no need to go any higher in wattage . . .

You got yourself some excellent recommendations provided by toyftw and looniam, too bad I wasn't in time to give one myself....damn skyrim eating up all my time  

Anyways keep below 650 watts, 650 is pretty much the tops for a single high end GPU (as far as I know), when you go over 650 you start to satisfy the needs of crossfired cards and overclocked systems.

Went for this one,

http://www.dabs.com/products/corsair-750w-gold-professi...

Thanks a lot everyone.