Hi Router
Here's a small tip for speaker boxes, install one or two holes (3" to 3 1/2" dia.) in the back of the box and put in some PVC tubing with a holding ring and a board inside the box between the speakers this will let the speakers move like they should also use silicone on all the joints inside the box then coat the inside the box with a white rubber base paint this will seal the box up.
This tip comes from my son that works at Car Toys
as a install Mrg.
I can't get into the size of the speaker box and it's one of the big things that comes into play with a high end speaker system.
Bj