Im playing on R9 270 although i never used a "heavy" ENB cause i prefer 60fps over eye candy.
Your GTX 960 is ALOT better than my card so i believe that you can use some decent ENB without any significant fps loss.
If you are interested on a really performance friendly ENB though look on Nexus for Reallike ENB. I was using this only because it made the colours more vibrant but dont expect any fancy effects , but i had almost zero performance loss.