^5 +1 what obsidian86 said. Fortron isn't known for high quality power supplies.
The general rule of thumb is a high quality 500 to 550 watt power supply with sufficient current (amps) on the 12 volt rail(s) can easily power a system with any single video card made. A high quality 700 to 750 watt power supply with sufficient current (amps) on the 12 volt rail(s) can power a system with two video cards operating in dual mode. There are a few exceptions like the new ATI Radeon HD 5XXX series cards which use less power due to their energy efficiency.
Before purchasing a new psu you will need to decide whether you will eventually have a pc with one or two video cards.
Corsair, PC Power & Cooling, and Seasonic are some of the brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Lately we've been seeing a few other brands offering some high quality units.
The main thing we need to know .. is how many AMPS are available using that PSU? Depending on the AMP output of the power supply, you may or may not be able to run the 260.
They say you need at least 38 total AMPS to run the card. I think that's a conservative estimate but it would be a good idea to have at least a 40 AMP PSU. The WATTAGE is there, for sure. That's a non-issue. So look and see how many total AMPS it's putting out. Should be on a sticker on the side of the unit.