Look up "SirGCal" on here or Google. He's a Mod on here (JF) I believe. He designed a sub box that functions as your rear seat. I got an old YJ rear bench for $10 and plan on converting mine into a single 12" box. Right now I'm running a cheapo sub box from Walmart and a Sony 2 channel amp (1000w) for all 4 speakers and sub. Sounds good at the moment but the box is a PIA to work around and had to add spacers between it and the tailgate for it to work.
A free people ought not only be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government. -George Washington