"The advantage to having all mains full range with mono bass is absolutely dramatic - much more LF power handling and solid low end that is uniform throughout the rather large room."
Tucker, I agree with you. While I don’t have five main, I have two Revel Ultima Salon 2s and a Ultima Voice 2 set a full range plus bass. I then have a Thiel 3 (now discontinued, I think) running a mono bass. This is a big subwoofer. My three rear speakers are the Thiel Powerplanes.
The bass is fantastic. As jlanzy says you get a powerful wave (I actually call it a bubble). It NOT a separate sound is one gigantic presence. Of course the room vibrates at times too, but it doesn’t sound like the exaggerated bass, that drowns out everything, that I have heard on some systems. I also came close to buying the B and Ws.
My room also has a cathedral ceiling, which creates an unusual illusion with the sound, making things like Superman really sound like he is flying high.
To be honest, I haven’t yet played much with equalization.