a 6950 is as good as the 6970 with a high OC.
and you can try to unlock the shaders of a 6950 too, making it equal to a 6970. it should work with 90% success.
of course, a 6970 is better performance right out of the box.
i dont think u can find any new reference cards to flash anymore. ive been looking havent seen 1 . your best bet is to get a sapphire toxic 2gb 6950 and maybe u can get one of those that sapphire already unlocked the extra shaders on them. my powercolor 2gb 6950 flashed, but not OC runs all games very smooth on 1080. 50fps+ on bf2 and bf3 beta.