You don't get good performance if the PSU is 264 watts.
Wattage does not tell the whole story these days.
There are 350W PSUs that are superior to some 500W variants. Manufacturer, weight, Amp distribution, noise & heat levels, ATX specification, form factor, modular connectors etc .... are all things that need not be overlooked when comtemplating a PSU purchase. Hardware, especially graphics cards must be considered.
Here is a good way to determine what one needs, based on the system being run.http://www.journeysystems.com/power_supply/