Dave, here's a thought: would you like to try an AutoTuba in your car? Bill Fitzmaurice sells the design and I built a pair but can't use them. They aren't enough for PA but one would pressurize a car pretty good. They're 14" x 14" x 30", have an 8" 4ohm driver, unfinished 1/2" Baltic, and I drive to Windsor every day.
Since you gave back the 2 Pis I'd trust you with one of these And whatever happened to that JBL-fueled 3-way monster? Looked like it just needed some crossover tweaks way back when...
I know you said