Hello all. So my buddy has a newer mazda miata and looking to upgrade the system. He wants sound quality and volume. Space is really limited. He picked out some polk components for the doors and is woondering what amp to buy. Also he said something about a sub box under the dash or something. The trunk is not an option as he fills it with stuff to take to the track. Anyone have any experience with this car or any advise would be great thanks.