This is my setup. I have the KLA subwoofer in the passenger side trunk well, and the amp in the spare tire well. The subwoofer just sits snuggly in the hole is is not secured in any other way. For the amp, I mounted a wooden board to the bolt hole that the spare tire attaches to. Then I screwed the feet of the amp to the board and used some foam on the top and bottom edge for added cushioning. It all works great, and you can't tell any of it is there! Next step I may add an amp to power my speakers, which I upgraded a long time ago, but just have them powered off the head-unit.
