I feel your pain. I just got my new sub amp last night and it's twice as big. The old one was 9" long this one is 18". It won't fit under the rear seat. At least not as the floor pan is now .

I hate to take a hammer to my floor pan but it sure is nice to have my amps hidden.

One bit of advice. Keep the amp as close as you can to the head unit to keep noise and ground loops to a minimum.