Personally...HD 6950 is not that bad. Maybe the fps could not satisfy u but if the game is smooth I think it's enough. Yes, waiting could be such annoying but I really don't think GTX 760 could make much difference on the real experience just on some meaningless increased fps. Neither is the HD 8xxx.
Anyway, if my answer still don't satisfy u, just go GTX 760 anyway. I don't think it would give u a big leap except for the number of the fps increased. (BTW, I am using FX-6300 + Yard Sale HD 6970...budget matters >3)