On multi-amp setups
My own quest has taken me toward increasing simplicity.
I never played out with a multiple amp rig, but did experiment with both amp switching and amp combining and quickly reached the conclusion that it was too complicated to balance multiple amps against one another. Differing amounts of compression and different EQs make it hard to balance the volumes. After several years of using many different channel switching amps, I reached the same conclusion regarding channel switchers.
Now I play with a single channel amp and no pedals, so I've given up the ability to go from clean to saturated gain. Much to my surprise, I don't miss having access to that much variation in gain.
For bluesy and jazzy stuff I plug into my Vibro-King and pluck mostly with my fingers. This gives me the ability to go from sparkling clean to mildly overdriven just by altering my touch on the strings. It's incredibly liberating to be able to throw in a quick single-note run that jumps to the front of the mix and then instantly drop back into the background for comping.
For the heavy music I plug my 1980 ES-335S (with overwound pickups) into the Mark IV. The channel-switching lets me get the big jumps from clean to saturated that I can't get with just a guitar into a single-channel amp. It's more a matter of supporting the musical style than it is a personal preference - a multi-channel amp is harder to set up and can be distracting during performance.
I'll tell you, I started out thinking that I absolutely needed the "flexibility" offered by pedals, channel switching, etc. As time went on, I realized that all those options actually detracted from my playing. Now it's just guitar into amp, and I've never been happier with my sound or my playing.