whats the best psu for this system and is modular better

Solution
Here are a few more options
XFX TS Series 550W Bronze efficiency, non-modular ~ £50
XFX XTR Series 550WGold efficiency, fully modular ~ £70
I did XFX first since they use SeaSonic as their manufacturer - they tend to be solid units
Antec High Current Gamer M 520W Bronze efficiency, Semi-modular ~£60 (another SeaSonic built unit)
About the least expensive PSU I would suggest (not really recommend) would be the EVGA 500W 80+ efficiency, non-modular this one is built by HEC ~£35 - review can be found here http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story6&reid=384 (linked to conclusion page)
A few more options anyway
Here are a few more options
XFX TS Series 550W Bronze efficiency, non-modular ~ £50
XFX XTR Series 550WGold efficiency, fully modular ~ £70
I did XFX first since they use SeaSonic as their manufacturer - they tend to be solid units
Antec High Current Gamer M 520W Bronze efficiency, Semi-modular ~£60 (another SeaSonic built unit)
About the least expensive PSU I would suggest (not really recommend) would be the EVGA 500W 80+ efficiency, non-modular this one is built by HEC ~£35 - review can be found here http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story6&reid=384 (linked to conclusion page)
A few more options anyway
 
Solution