My response (editted it) to a very simular post about an hour ago about the 550ti vs the 650.
An Alternative would be the Newer AMD 7770. If you look at the top of the Link (Heading GPU12) you can select which two GPUs to compare. Higher FPS,
only slightly more power – 250W which is only 19W more than 650 but 36 Watts lower than 550 ti http://www.anandtech.com/bench/Product/536?vs=680
This link shows FPS for a LARGE number of Games and at various Resolutions. NOTE: Not many game at 1920 x 1200 (16:10)http://www.anandtech.com/bench/Product/536?vs=681Performance vs Cost, Based on US Newegg prices, Unless $20 is a deal breaker then the 7770 is a clear winner.
Added would agree the 650ti would be better than the 7770http://www.anandtech.com/bench/Product/536?vs=680
But then you also get into for just a little more than the 660ti you have the 7850 BUT 7850 jumps cost upto $170->$200:http://www.anandtech.com/bench/Product/549?vs=680