Here's a list of the latest gpu power requirements. What's more important than the wattage of the psu is the amount of amps on the 12 volt rail. Most psu's have multiple 12 volt rails. You need to add the amps on each rail to see what you have. Ideally, a psu with a single 12 volt rail carrying 30 or more amps on the rail would be better. List your psu specs. You can find them on the label on the side of your psu.
Then look at this page for suggestions.