The Bose subs are $299 each and the system is at full power with 2 connected, so I'm guessing that he also used 2 addon amps ( Bose are $299 each too)
So, he has $3000 invested in bass alone. The up side is that he only has to carry teeny, tiny cabinets in and out of the job.
At my age, I'll never hoof a 75lb monster in to any room for any reason.
The more cabinets you add more than doubles the bass output. When you stack to cabinets on top of one another, you get 4 times the sound.