I have a custom built Box for a 10" subwoofer and an amp rack. They are built by Mr. Marv and I bought it from another member, but I never used it. The box and amp rack are sprayed with bedliner and they will mount behind the rear passenger seat after you remove the storage rack.
I do not have any pictures of it installed since I never used it.
The subwoofer is a Rockford Fosgate P3 10" slim mount. Here are the specs:
I prefer local pick up, but I will ship at your cost.