It certainly sounds exactly like a failing/failed power supply from what I've seen and personal experience. I was unable to find any wattage tech docs online for your psu. A simple check with a multimeter should tell. See:
To get a better understanding of the new ratings, spend a few minutes reading
Picking The Right Power Supply: What You Should Know
PSU pricing varies on where you live. In the states, newegg sells a lot of hardware. Read their customer reviews to get a good idea of quality.