Not too concerned with the actualy box design, that can always be edited. You have plenty of net airspace to work with.
With 8 12s, you are going to be looking at 12-14ft3 of total net airspace. Depending on which sub you go with and how much power you are running.
8 Level 3 12s built with the Level 4 coil and a 10k to power them would make for one very nice wall.