it is for any psu that has the proper connectors (no adapters for the gpu, a good way of determining if the psu will power your system (only exception would be the sata connectors...))
the gtx660 uses approx 180 watts max. (msi gtx660 hawk) so any GOOD/excellent power supply that can supply your system and Peripherals + 180 watts will do.
problem that when you get with in 80% of the psu's power, the heat generated by the PSU becomes a problem (thus the noisy fans on PSU's)... (the stuff in CHEAP psu's tends to burn-up...) (to bad tomshardware can not torture cheap psu's to see of they fail (how long does ot take for a CHEAP psu to burn out at maximum wattage...? or even a 24 hour torture test of max wattage at 50, 40, 30 degrees ambient...? why?... a review site does mot get far wrecking equipment that they get for free, and if they pay for it, why destroy it?... )
TL;DR ... as long as the psu has connectors for the GPU, no problems... otherwise the quality and amount of power the psu can supply when using adapters is needs to be questioned, so a Power Meter would be a good idea to determine hw much power is being drawn.