dang that looks like its gonna be sweet. I wish I could find someone who wanted me to build something like that or understand enough of box design to be able to design it.
Can't wait to see the construction. Gonna need some lights in that thing too just so ya can see the subs when it is all done.
Any way you can possible brace the center span externally so you don't need those 2 center braces? They look like 2x4's and I'm sure you could finish them to blend in nicely and such but I think it would look 100x better without them in there for when people go to check out the subs and such.