I paired a 6670 with my A10-6800K. I wasn't satisfied, so I exchanged it for the HD 7770.
the HD 7770 hands down outperforms in every way an A10-6800K in dual graphics mode with an HD 6670. Also, not every game will utilize the dual graphics, so the dedicated HD 7770 is really going to smoke the 6670 in those.
If you can get the 7770 in your budget, do it. I just continued to use my integrated graphics until I could afford it, and it was worth the wait.