Comparison of various subwoofers for 2 channel audio

One thing i've noticed with subwoofers.  there are two types of listeners:  those adding subs just to make the bass natural--the way it was recorded.  And then there are those who want more bass than is recorded on the track.  I'm not criticizing anyone but these discussions go sideways as the two different crowds have 2 different answers.  It is good to define which you are.

Jerry

How is the bass in the main listening position? Most rooms only need two subs for even bass optimized for a single seat. More is always better but may not be need.

Far more important is how are you going to control 4 subs? Are you going to crossover to them (highpass) Keep them all the same distance from the main seat? If they are not the same distance time delays will be needed. 
 

all the subs you mentioned are fine. I would just buy another  212 as it is a great sub too. My only issue with SVS is the very high group delay. It might be hard to tune those with electrostatic speakers. I personally would look at Rythmic in your list. The F18s are a great buy, and yes bigger is always better…

It’s really hard to see going wrong with a couple Rhythmik F12G subs and along with your MLs should be quite something using all four.  FWIW, and best of luck.