I'd get an R9 290 and overclock it before I got a 970. A SLIGHTLY overclocked 290 beats a 970, I think stock it does as well. I know the 970 is not far behind, though. Same VRAM, same/better performance, less cost.
(I'm basing this off benchmarks I've seen, as a 290x was getting better performance than a 970, and a 290x is only 5% faster than a 290, a margin easily met with small overclocks)
To be honest STRIX cards are overpriced garbage, they raise the VRAM to levels you won't even need/use and put slight overclocks on the cards, all for $150+ extra cost. Although the 970 and 980 STRIX cards COULD be a different story, as I'm not sure of pricing/performance. All I know is that the 780 STRIX is a waste of money unless you're tying for like 4K/5K multimonitor gaming
But if it's power you're going for, the 970 definitely takes less. Although if your PSU can't handle one R9 290 in your system it's time for an upgrade, past time really. Now if you plan on going dual GPU (SLi, Crossfire) the 970 is a better choice unless you have an 1100W+ PSU.