Im planning on replacing the stock head unit with an in dash dvd receiver with screen..

Replacing the front stock speakers with a decent 6-1/2" component system..

Is there a way I can keep the factory amp to use with the speakers? or will it ruin the sound?

And swapping the "subs" for a pair of 6-1/2" 2-way speakers..

and put a sub/amp in the cargo area..

Sound like a solid idea?