Actually the more I look over it a 650Ti isn't even worth it. It's not really an upgrade at all. The GTX660 is a small upgrade. You would almost have to go to a 660Ti to make it worth any sort of decent upgrade. They are about $290-$300 with some having MIRs.
Page through this review. It has the 560Ti, 660, and 660Ti in the charts. http://www.anandtech.com/show/6276/nvidia-geforce-gtx-660-review-gk106-rounds-out-the-kepler-family
I'd just sit on your 560Ti for now. Maybe try your hand at overclocking. I know they are very capable of it with good performance increases.