If you are too lazy to make a box buy one you dont want to make angle so buy one it's much better with the angle take less space (maybe it's nor your case but general facts) and has more style than a rectangular one.
I also seen boxes with internal division well that's hard to build and I'm not sure of the efficienty.. (my opinion : Get a 12 " Type R it's just so AMAZING I heard a GTS Celica that lives 3 streets in front of me and the bass was just COOL. It's also cool in the car
)
-My opinion.