The brand of the PSU is very important, actually. The PSU is generally considered (or should be) the most important piece of hardware in any build. A no-name PSU can actually damage your other components with voltage fluctuations, and some can actually explode. We need to know what yours is.
Get MSI Afterburner
. It has a stress tester that will display the GPU's temperature while pushing your card just about to its limit.