The Coleman Audio SPK5+1 Speaker Switcher really adds a practical way to switch between monitor speakers, both passive & active pairs. I only have two pairs connected right now, so I use one of the empty channels to go to when I want the system muted in the control room, due to an open mic.
It is built like a tank, with superior quality workmanship and materials, however, I had to downgrade it a bit because there is no allowance for "muting" or delaying the THUMP created when switching "live" between pairs of monitors. My previous switcher did allow for this, and did not create the potentially damaging cone THUMP when speakers are being switched quickly for an A-B comparison.
I would think this would've been key in the design of a monitor switching unit, since as engineers, we always need to switch "on-the-fly" to quickly assess our mixes.