The only advantage of getting a GTX960 is the lower power draw and resulting heat. The GTX 970 is much faster and will take a less noticeable performance hit when streaming using the Nvidia encoding tool (don't remember the name). On the other hand you will only notice the difference of 4770k vs the 4790k in bencmarks.
To sum it up:
- if you value fast graphics and high quality settings, as most gamers do, get the GTX970 + 4770k;
- if you value quiet and low power PC with a more powerful CPU (as i did with mine GTX960 + 4690k), get the GTX960 + 4790k.