I agonized about this very thing when I decided to install my current system. 4 crossovers, 2 on each side of the rear passenger seats under the carpet. Affixed with velcro. It's otherwise unuseable space. In my 3rd Gen, the carpet just bulges out a bit but still tucks under the door sill. You'd never know they were there. Also, I'm not using any of the factory wiring.