XFX nvidia GTX 260 required power supply?

500w Seasonic will be fine. Geforce always gives a higher PSU wattage requirement than is really required just to cover themselves against claims from bozos who might try to use an existing low wattage PSU which, if it fails under load, can nuke the card.

By "low wattage" I mean some ridiculously feeble 250w or 300w low-quality one (yes, there are some who try to get away with one of those after a GPU upgrade for gaming. I kid you not).