A quality PSU should handle the GTX 260 fine. As long as it's not some questionable peace of junk that was rated for peak output in a freezer. Never put hardware you care about on cheap dirty power.
IMO a Coolermaster igreen 600w should be perfectly fine for the 260.
The draw for an i7 system
@ 3.2GHz with a GTX 275 installed is listed below-
Those numbers are not card consumption only.