Behind the wall is the gas tank. Killing the amp is easy with a switch on the remote turn on lead (think 12v switched output off the receiver in your home theater or power center that triggers stuff like a projection screen ect.). Depth of the box and woofer will be tough, although there are some challow woofers from pioneer and kenwood that are around 3" or less...my expereince in cars with them had not been good...think Lotus but if that is the only solution then go for it. You might want to consider an infinity basslink if you are trying to keep it small but want some extra oomph.