I am thinking about getting a GTX 960 in a month. The plan was to replace my current 660 with it and use it for 4k dsr gaming to 1080p and maxed quality settings for certain games, and also use it for making music videos on premeire pro and after effects plus a bit of photo editng on photoshop. I noticed that the memory bit interface is 128-bit on the 960 but the 660 is 192-bit. Will I see any performance gain from playback to exporting speed going from 660 to 960? Thanks for the help in advance!!!!
4k dsr gaming to 1080p and maxed quality settings
depending which games you are talking about, you would need the gtx 980 ti to do that and get good fps. you may want to consider the gtx 970 at least. if you go with the gtx 960, get a 4gb version.
for premiere, you might see slight improvement, will depend on which and how many gpu effects you are using.