Mark III as a One channel amp and never look back

Had my share of Mark III's and some Mark IV's.
Currently have 2 red stripe III's, one combo & one head.
I can get literally any tone out of my III's as long as I use them as I ONE channel amp.
My experience is the clean & lead channel can kinda share the same EQ settings. R2 needs it's own EQ.
R2 pushes more midrange than the other channels and naturally eq's out some low end.
I have the R2 mod on one and it doesn't really help anything since R2 has a different EQ from the start.
I wish I would have spent more time 20 plus years ago approaching a Mark III this way.
All 3 channels completely kick ***, just not as a multi channel amp for me. I'll use an OD pedal for solo boosts live and studio too.
Get one with a GEQ. If not, use a tube screamer type pedal for a boost and you'll be happy with your tone.

I do the same thing with my Mark II's and a MESA amp switcher. Any thing else is a compromise one way or another.

I don't consider the MkIII as a 3-channel amp, but rather a 1-channel amp with 3 footswitchable modes. In fact, the Mesa/Boogie Operating Instructions calls the commonly referred to "channels" modes too. I.e. "Fender mode", "Marshall mode" and "MESA-Boogie" mode.

Yup, this. I could call it a viable two-channel amp between R1 and R2 if the Deep pull was footswitchable.

One thing I have noticed though, don't be afraid to turn that mid knob right down. Several old Mesa manuals (both my Marks and my Tverb head) have sample settings with mids at 0, which is definitely out of fashion these days. But pulling out the mids via the knob changes the 'focus' of the Treble and Bass controls so that a lot of that characteristic Mark 'honk' (or 'plinkiness' on the cleans) backs off without sounding scooped, and gives you some decently switchable sounds with a little EQ tweaking.

Channel switching amps are anyhow overrated! The lead channel on mk3 alone already covers everything i need. It cleans up just fine. I do like the cleans quite a bit but clean clean is not something i have use for. Over the years i’ve had up to 4 channel amps and it’s always one or two base sounds i use during a show (not including fx). To balance all the channels especially running 2 amp setups is something i dont fancy. You end up with something during soundcheck and when the fat is in, everything changes. It’s liberating to operate with one sound and in that scenario mk3 excels.

I never have any use for R2. I do use the clean and lead channels.