I could get technical here, it is to easy for me to do, so I will not.
Simply put, some people spend time educating themselves on CPUs and video cards, however the vast majority of computer users have no clue how important it is to get a good power supply and why. Go to www.jonnyguru.com to look for reviews of a PSU that you find interesting; note that if a 650 watt version of a power supply has a great review then most of the time the other power supplies in that line with higher wattage will also be good even if there is no review. And, to make things worse the cost of power supplies has gone up.
You may have to eat the cost of that power supply. You need a new one before that one destroys your computer, and I mean that...