Hello, I have gone through some threads here about choosing psus..i found some new things besides Watts....and i found that for those factors in some cases a 600w is better than a 750w.rail voltage is also one factor.would anyone plz explain what are they?a link can be very helpful..i'm not changing my psu soon but want to know what things to see besides watts before buying a gaming rig's power supply.thanks in advance.