Strix 970 and some other 970 cards use only one 8 pin power connector which is fairly frugal compared to other options. This give you about 90 to 95% of max 970 performance without burning a ton of watts. Find a deal on one and enjoy playing games now without using a ton of power. Then you can see who comes out ahead in the Pascal/Polaris battle later this year and resell of the 970 if either card is dramatically faster.
If you wait long enough, Kaby Lake CPUs will come out and you will really be kicking yourself if you bought that CPU and never really used it before a new faster and more efficient CPUs were out
Also GPU power usage won't really affect your power bill much, though I understand your desire to use efficient components in the PC. I recently switched my entire house over to LED lights, bought a smart home thermostat, switch to an LED monitor, got a new Skylake i5 PC, replace some appliances with newer Energy Star models, and got a new 80 Plus Gold power supply. Every change was small, but the overall effect on lower power and heating fuel usage is nice.