did you switch out entire sub / enclosures as a whole, or remove the subs from their enclosures and swap them to the different boxes for your comparison testing?
Some cars have better acoustics than others. I used to have a t1 that sounded amazing in my car but then we switched the sub box amp wires and head unit to another car and it sounded like ****. Also if youre looking for quality, don't go kicker.