PSU is the power supply unit. the thing all the power cables connect to it should have something like maximum output 600w or even a make and model would be good. the pool your using should be fine just check the settings on there website with the ones that are in guiminer
I have a 'be quiet! System Power S6 550W ATX22'
so it seems when it is under a lot of stress it powers down my GFC
and what do you mean by 'even a make model would be good'?