Hiper HPU-4M580

For your system (with Crossfire) I'd recommend 650-750W, especially if you're going to over clock. 580W sounds like you maybe be maxing the PSU out, which will shorten it's lifespan. Just give your self a little overhead as per the wattage I suggested above.

I feel that I should mention Hiper is one tier 4 of the PSU listings (Found here: http://www.tomswiki.com/page/Tiered+PSU+Listings?t=anon ) which generally means they aren't too great. So, if it's in your budget, you may want to consider a PC Power & Cooling Silencer 750 or something along those lines.

Ah, thanks a lot, ill have a look now. If i cant find anything ill go with a 630 or 670 watt hiper as my brother has used one for about a year now and hes had no problems at all. But as you pointed out they are tier 4 ill check out what you suggested!

Update: The only PC Power i can afford is the 610W one, http://www.overclockers.co.uk/showproduct.php?prodid=CA-002-PP&groupid=701&catid=123&subcat=928. Ill check out some of the other Tier 1 PSUs off that site, but im guessing all are expensive so i may go with a Tier 2.

Update2: The only PSUs i can afford from Tiers 1 and 2 are the one linked above, and this OCZ GameXStream, http://www.overclockers.co.uk/showproduct.php?prodid=CA-018-OC&groupid=701&catid=123&subcat=148. As you can see for the same price as the 680W hiper i will get either a 610W or a 600W. If the Tier 1 and 2 PSUs really are that much better i guess ill just have to hope that they dont burn out too fast!

Als, on overclockers, all the Hiper PSUs that are rated are given 4.5-5 stars (the one that has a 3 star rating is just beacuse they dont like the fact that the mains plug is modular...idiots).

I'd almost prefer modular cables as long as the PSU is still reliable. It makes for a lot less clutter, better airflow, and that means... better temps.  

680W Hiper it is then! More give on the wattage, modular and my brother has had a good experience with them!

Thanks a lot for your help!