Realistically, what would lower power consumption actually do for you? Reduce your bills by a couple bucks per year, at most? As long as you have the PSU capacity the power consumption is pretty irrelevant between a 960 and a 7870 XT.
Better to evaluate it from a pure performance and price perspective. A 960 would be a little faster than the 7870 XT (i.e. 7930) but if you're going to upgrade, I wouldn't get such a small "upgrade." I'd shoot for something in the R9 290 /GTX 970 range of performance so the upgrade feels like a big upgrade. Besides, for $70 than a 960 more you can jump to a R9 290 which is significantly faster. 960 is really bad perf/$. New cards coming out soon, so it's probably best to wait until the end of Spring and see how the market looks then. Both the 960 and R9 285 are pretty poor products at their price points -- the midrange is suffering right now. Hopefully it will get better when the new lineups hit
I bet we'll see a solid 370/370x chip that will be a good upgrade as well as a GTX 965 or 960 Ti or something like that, that isn't 128-bit and 2GB of RAM...