well, I cannot visualize what the back of your seats look like, or if the seats are fabric, leather, etc. But an old school trick is to cut the foam out of the seat and use seat belt straps across the void tied to the metal seat framework, like this:'a couple of 12s' is the problem. Which 12s would be louder than my Fi that meets my space requirements. Idc about sealed or ported if it all sounds right. Back seats also do not go down