As for slim chassis subs, you have a number of choices. Many of the big name companies make them. JL audio, MTX, Pioneer, Boston Acoustics, Rockford Fostage, and Kicker just to name a few. We at my brothers shop have installed the JL Audio and Pioneer shallow mount subs in a few trucks and the sound great. We built a box to mount the subs behind the seats and mounted the amps in the middle. Those subs are very shallow so you can make a very shallow box, they also don't need a lot of box volume so the box doesn't have to be enormous.