Google sub in rear seat jeep wrangler.
Neat approach, I have never heard one though.
I know a lot of people think 100's of watts of power and even 1-10 inch woofer in ANY car seems like overkill, just keep this in mind, in your car/truck you have to overcome many issues that are not present in your home.
1. Speaker placement is terrible,you are way to close to the left channel and the sub is usually behind you.
2. The noise floor that you must overcome is drastically higher than your home. Wind noise, road noise, tire noise etc...
3. The environment is just about as bad as it can get for quality listening. Most of us overcome this with sheer volume.
I have listened to some truly amazing sounding cars, but when it comes to sound quality most can't rival a quality 2 channel amp connected to a midline pair of speakers in a house.