When I went over 2 pairs of speakers and wanted to try bi- or even tri-amping with an addition of a sub is when I considered a distribution amp, beyond the disdain of the purists.
Now, with 6 discrete amps on a single chassis, each of which can be driven separately or driven by a common input.
Each can be switched to mono separately; each can drive 2 pairs of speakers with it's own levels or even discrete delay if desired.
Perhaps not SOTA, but 'clean enough' with no real differences between the amps' output qualities...and a common line out if one has to have More....
One can spend the rough equivalent of a decent one in/two out for new, or get a used for substantially less. And each amp had it's own protection circuit if you get too frisky.... ;)
But...to each...