What do you think about this setup?
 

I have a 07 Coupe, Infinity system w/ navigation. I got my head unit installed and of course I lost sound from the 2 rear speakers. And now I miss them. I'm thinking about getting the rear speakers replaced with the 6" kicker subs and using a 2 channel amp to run them. I'll let the head unit push the front speakers.

If I do this mod, will I still be able to go with the setup I mentioned earlier?

Is the earlier setup worth doing?