JBL system

After looking at literary 10's of threads about uprating the JBL 9 speaker system, I just have 1 or 2 questions?

If I place a power amp after the JBL amp, using appropriate signal summing device for the fronts and rears, will I loose the Bluetooth/nav voice? all speakers will be uprated also.

Is it as easy as just using the audiocontrol LC8 and changing the speakers/adding an amp?

My aim is to have 1 x 10" subs in the boot, 8" kick bass in the rear doors and 6 1/2" components in the front. Keeping overall current draw as low as possible - don't want to over load the inverter. i also need to keep the Bluetooth phone and nav. I am going to be using the existing wiring to each door.