I have mounted the amps in the area for the cd changer and left the sub-box, by ads two 10" in sealed box, right behind the rear seats, and still have reasonable space left.
About the rear roof speakers, they are easy to replace and run the wires. If I remember correctly, factory wire run in the c-pillers to the roof then back to the speakers.
What do you mean by ICE equipment? Does it let you connect aftermarket cd changer to factory head unit?