Need help deciding on psu

[PILLAGER]

ive got £50 to buy a psu and i need to know which is best of these 4 from scans website all around £50 or if you know a better site tell me

http://www.scan.co.uk/Products/530W-Be-Quiet-PurePower-L7-CrossFire-SLi-Ready-80plusATX-23-Dual-Rail-12v-2x6plus2Pin5xSata4xMolex

http://www.scan.co.uk/Products/500w-Silverpower-SP-SS-500-Green-Power-80-Plus-CertifiedIntel-ATX-12V-6Serial-ATA

http://www.scan.co.uk/Products/500W-Silverstone-Strider-ST50F-v3-Silent-120mm-Fan-Dual-plus12V-80plus-Eff

http://www.scan.co.uk/Products/550W-Coolermaster-GX-SLI-CrossFire-85-Eff-120mm-Fan-EPS-12V-20plus4-Pin-5-Year-Warranty

ive got a 4850 card and i might get another to crossfire it if these psus can handle it

 

[o1die]

Only brand I've heard of is coolermaster. It's not a tier one manufacturer, but your video card doesn't require any special ps. I would look up the specs of the 12v rails on coolermaster's website before ordering if you want to add another card later. I wouldn't go under 22 amps on the 12v rail. The best ps are made by corsair, seasonic, antec, and enermax in the usa. Don't know if any of these brands are sold by your vender.

 

[mosox]

Out of those I would get the Silverpower, great PSU. Silverstone is very good as well.

 

[davcon]

^+1 Silverstone makes good units.
For a bit more you could get a modular one that's crossfire/sli rated.
Silverstone Tech. Strider 500 W-£53.45
http://www.scan.co.uk/Products/500W-ST50F-230-v-10-Strider-PSU-silent-modular-cable-V-10