The MMG plus the DWM bass module is called the Super MMG. The MG 12 is a different speaker altogether. It's bigger, with a larger radiating surface. The MG 12 is 17.5"w x 51"h x 1.5"d and has 329 sq. inches of radiating diaphragm. The MMG is 48"h x 14.5"w x 1.25"d, so its radiating diaphragm is probably around 220 sq. inches.
07-16-14: Larrybou
I had the impression the MG 12 was basically the MMG plus their bass module. A Mag dealer told me the MG 12 usually still needs a subwoofer, so it's a better deal to get the MMG with a REL sub and have more versatility and bass response. Not true?
A REL is certainly not the only option for fleshing out the bass. Maggie's DWM panel offers some advantages, such as transient response as fast as the MMGs, reasonable price, versatile placement, etc. For a conventional sub, REL is certainly not the only kid on the block. My little Mirage MM8 subs are perfect for my 1.7s, but unfortunately most Mirage is now out of production. Still, there are other offerings from Velodyne, Paradigm, Def Tech, PSB, etc. that may make for an easier blend than the REL.
I say this because the other subs I mentioned have a more extended, flatter frequency response. The REL T-5, for example, contributes a sharp, resonance-driven spike, and relies on corner or wall placement to excite room modes to broaden the frequency curve. I like subs that don't rely so much on that because it makes it easier to blend the sub's timing iwth the panels. I have my little subs sitting right next to their panels, and don't have to fuss with the phase knobs. The integration is seamless.