After reading for quite a while over at "the Cult" and doing some figures I decided IB was an interesting choice for me. However after adding on to the house and building a shared room for recording music and a dance studio for my wife to teach dance class. I didn't have the funds to buy the sugggested 4-15's and a pro amp to drive it. Project put on hold.
Fast forward a few months and I was browsing at a yard sale. I found a pair of Jensen "monkey coffin" speakers and an integreted amp, $25 for both. The speakers didn't sound like much, what with them being built out of 1/2" particle board with no bracing. but they had 15's in them.
I removed the speakers and threw those cabs away. then built my own baffles out of 2 layers of 3/4" plywood. put the pair of 15's in the attic wall, hooked up the amp and crossover and wow!!
Those cheap speakers play louder and lower than most of the box subwoofers I've heard. I am converted. Since the room is used as a music rehearsal space and dance studio, taking up no floor space is a big bonus.