I'd say it's time for a new PSU no matter which way you look at it. Sounds like it is very old and outdated. And more than likely severely underpowered. Older PSU's tended to have less wattage anyway because all of these power hungry GPU's weren't available.
UPDATE: I was going through my older posts and noticed that I recommended a new PSU, but I didn't exactly say what kind. I recommend that you go with Corsair AX, AXi, RM, CS, or TX. There are rumors that the RM series has faulty secondary capacitors, but I have researched it and have found NOTHING to back that up. The AX and especially the AXi series by Corsair are as good as it gets in the PSU department. Both are "80 Plus Platinum rated, and the AXi (ONLY the AXi, not the AX) series is the only digitally controlled PSU on the market. The AXi (again ONLY the AXi, not the AX) also comes with a Corsair Link module, which along with the Corsair Link dashboard software (Corsair Link software is available as a free download from Corsair's site) gives you the ability to monitor/tweak your PSU in many different ways, including the fan. The AX and AXi both come with an industry leading 7 year warranty. You may as well call this a lifetime warranty because no one who games keeps a computer for more than 7 years. (I assume you game because of the high-end GPU)
You will pay more for a Corsair, but you get what you pay for. I own a Corsair AX860i and absolutely love it.