Basically, yes. GTX 660 is the minimum requirement for GPU while GTX 960 is recommended GPU for Sniper Elite 4.
Do note that GPU power doesn't follow the same rule as GPU naming goes.
Example: GTX 660 (let's say it's low end) -> GTX 780 (may think that it's medium end) -> GTX 960 (sounds like it's the best than 2 previous ones). But that is not a case.
Basically, yes. GTX 660 is the minimum requirement for GPU while GTX 960 is recommended GPU for Sniper Elite 4.
Do note that GPU power doesn't follow the same rule as GPU naming goes.
Example: GTX 660 (let's say it's low end) -> GTX 780 (may think that it's medium end) -> GTX 960 (sounds like it's the best than 2 previous ones). But that is not a case.