I installed 4 near each corner, but not in the corner. We had a few stud bays to work with, so I had some choice as to where to place them. I have 4 of the 12 sub modules.
I love them for music. I have an all BG system, and set the x-over on the BG-X's at 100hz, so the kick drum sounds great on live shows. The only problem is on ultra deep, ultra dynamic movie passages - sometimes the subs just cant keep up. I probably run my subs a little hot after years of playing drums in live shows next to 18" drum fill subs. I enjoy the low end, basically. In a 2300 cubic foot room, I think 6 of the BG-X subs would probably meet the 2 or so db increase I could use for movies.
The beauty of the system is that the bass sounds great in the room, but doesnt resonate outside of the house. We rock concert blu rays until 3 am whenever we want!