After re-reading Bernie's post, I think he has something there.

Yes, if you are using a stereo mixer you could make things easier by just running right and left. But then the question of inputs becomes moot, as you are using the mixer for all your inputs. the CM-30 allows you to use ALL the inputs on both amps and have them linked together, technically eliminating the need for an additional mixer. As Donny said, the description on pg. 10 of the manual explains that. I think it takes a little "thinking it thru" to absorb their simplified explanation.

As per my previous post, if you get to the point where you are using up the inputs, I would hope you have devised a plan to bundle your cords, especially if you've got the CM-30s up on mic stands.