nVidia GPU naming can be confusing. But yes, you have a GK106 part(as is the 650 Ti), but the 660 Ti is different. It's a GK104, like the GTX 680 and 670; but with even more of the board disabled(some say broken) than the 670(which itself prob wasn't a good enough yeild to be a 680).
Anyway the 660 Ti is still rated ~20 percent more powerful(graphically) than a 660. But uses only 10 more watts(~7%). 150 watts vs. 140 watts.
GK 106 = 2.5 billion transistors
GK 104 = 3.5 billion transistors
GK 110(Titan) = 7.1 billion transistors
and then there is core clock speed(s), memory speed, memory bandwidth, ect...