I have a 760 and I could play watchdogs on ultra and that is around the same performance as the 660ti i think. The main performance hit is when you turn up the texture details, the normal graphics settings didn't hit too hard on the performance but as soon as I turned up the texture details on the display menu the fps took a big hit and the lag spikes that occur in this game seem to get worse the higher the texture detail is. So there you go, i could play ultra settings but with only medium texture details on my 760, take what you will from that