When I used to go to car shows back in England, I tricked out the rear of my 1981 Capri. Two 10" Infinity woofers in a custom designed box, component speakers in the door, and an amp rack with two Jensen amps. I did think about taking the amps apart and painting them yellow to go with the yellow and black colour scheme of my car, but never did.
More pictures here.
Fast forward 15 or so years, and I still have one of those Jensen amps, and it's still working fine. Nowadays, I try to use woofers that don't need a huge box, so I still have some trunk space left. Also, with more modern head units, especially ones with high pass filters built in, I find I can get away with using the amps in the head unit for the full range speakers, and just using an amp for the subwoofer.