You should choose PSU wattage according to your specs and your plans for further upgrades (specially the VGA)
Use one of these PSU calculators: http://support.asus.com/powersupply.aspx
http://www.msi.com/service/power-supply-calculator/
Get a Corsair or OCZ. Seasonic is as good as them too.
BTW, "CORSAIR Enthusiast Series TX650M 650W" is great for overclock and it's 650W.
i can find some ocz psus from the store i'm buying with discounts right now like the ocz zt series 550/650/750 watt for ~77/90/91 euros should i get ocz in case that something happens i'll have any problem with the guarantee now that ocz is bankrupt?