Thats the recommended PSU required for your system, you could in theory run a 430w PSU like this one below:
http://www.overclockers.co.uk/showproduct.php?prodid=CA-033-CS&groupid=701&catid=123&subcat=1084
But I would prefer a little more room![]()
A little more head room is always the better, because you don't have to invest in another PSU if you ever upgrade that is a little more power hungry 
