the box my 15 is in was for an 18' but he gave up and put another layer of wood to fit his 15 then he got another box and gave me his box so i have a huge box in my trunk and the 15' is being powered by..Kole Audio
Other than removing the rearview, there really isn't much that can be done about that. It's the price you have to pay if you want to start pushing heavy bass, just get used to adjusting your mirror all the time.