iknowhowtofixit :
AMD stopped production on the HD6970. None are available on Newegg right now. The HD7950 makes the most sense as there is not $100 more worth of performance between the HD7950 and HD7970.
7950 is 100 more than 6970, 7970 is 100 more 7950.
FPS wise in most games the 7970 is a bigger jump over 7950 than 7950 is over 6970, of course that is FPS wise. I am not taking into account the fact that the 7000s runs much more power efficient (thus OCing will widen the gap)
Honestly if we WAS interested in the 6970 than the 6870 is the most logical choice, it is the same price and is a good 15% more power with 33% less power.
OP-If I was still in the market to build I would do one of 2 things.
1. Get an I5 2500k and 1x 7870 (with plans to get a 2nd one after kepler and likely pricedrops)
2. Would wait til april to see what Keplar and IB brings to the table, most likely getting a 2550k for 235, and a 7870 (possible at a lower price) unless kepler really blows off the barn doors (then I would go with a 600s Nvidia)
Personally with IB being focused on graphics and 2500k being such a lush cpu, and with 7870/50 right around the corner I would go with option one, unless my current rig was still doing the job, then maybe I would show some patentience