If i add a 7770 vapor x to a A10-5800k, will the gpu in the apu help somehow the graphics processing or it will just deavtivate the Apu's gpu?

i know you can do crossfire with other cards like the 6670 but i want to know what happens if you add a higher end card 

The APU's gpu will be deactivated so you will only have the 7770. The highest card that can crossfire with APU right now is 7750 with a10-6800k.