Gene, with that many subwoofers, it may not be needed, especially with four subwoofers!
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
The main benefits in using the MBM-12 (or multiples of them) and letting the true subwoofers handle 50Hz and below with that system would be for even lower IM distortion and even wider dynamic range, but then again we're talking about something way overkill here