Well, that's the thing with a diy sub, you have to be happy with your finish/finishing skills, so I think you're almost there. The assembly is easy, while clamps are nice people have done this sort of cnc-cut flatpack assembly with something as basic as masking tape to hold it together while the glue dries, but perhaps you can simply borrow some? Cutting a terminal cup surely a friend with a forstner bit (what I use to install my preferred speakon terminal) or jigsaw or something can be found....maybe same guy with clamps
Finishing with paint is one way, duratex isn't a bad way to go either.
ps shipping for assembled boxes aside from additional expense, also opens them up to further chances of damage in handling IMO.
