I have an i7-960 and a GTX 660 FTW currently. I was wondering if I should upgrade the CPU to an i7-3770S with a new motherboard of course, or upgrade the GPU to a GTX 770. Thanks.
Here some benchmark between i7 950 vs 3770K. your 960 would be faster and 3770S would be slower.
http://anandtech.com/show/7189/choosing-a-gaming-cpu-september-2013
But remember that all techs are getting old. I mean his CPU which is about 3 years old won't perform as good as his CPU 3 years ago.
But still this CPU should still be very good and perform well... You can try it. Run a game and check GPU/CPU activity. Let us know what happened.
Here some benchmark between i7 950 vs 3770K. your 960 would be faster and 3770S would be slower.
http://anandtech.com/show/7189/choosing-a-gaming-cpu-september-2013
Ur cpu is still good, upgrade gpu. AMD is going to release new generation of gpu next week so if u can wait u will have some more options and prices will go down.