If you're using a pretty poor power supply, is there a chance that it might not be supplying enough power to your graphics card, and thus leaving you with sub-par performance?
Well, not really sub-par performance. It will either fail or not; it won't run slowly. Getting a better PSU will not increase your framerates, but it may keep you from crashing.
A poor PSU can definitely damage your components with power surges etc, and it probably won't supply the wattage it advertises. Get a decent, mainstream, branded PSU.
pretty poor power supply cause damage hardware like DVD RW (it will damage first) VGa CArd, HDD, Motherboard. and if you turn on PC your system automaticlly Freeze or restart and restart.
One of the indications of inadequate power is a system that will run a 2D desktop with no problems, but cause seemingly random reset/reboot cycles while gaming.
Power requirements of graphics cards can more than double under 3D gaming loads.