Purely interms of performance it's not a bad recommendation, though the GTX650 does have a small performance lead (it was initially averaging 5% slower than the GTX550 Ti but Kepler driver optimisation has put GTX650 in the lead by ~5%). Problem is power consumption. The GTX550 Ti has a TDP of 116 watts - actually more than the GTX650 Ti! The GTX650 is rated at 65 watts, so exceptionally energy-efficient (as you'd expect from the Kepler architecture vs Fermi).