Newbie again.
From pictures and dimensionsit looks like they may be rackmountable. Yes? Does it come with rackmount ears?

Also: think about three of them. Can I put three together one atop the other without hum or interference etc. And.....can I use the low voltage "activation" with three? Manual confusing?

Can I absolutely power down and not use the low-voltage? like if I wanted to go with five M200s.

There are rackmount ears available (see this page for the ears used with most rack-mounted M200's and this thread for a detailed discussion of rack mounting M200's).

Outlaw has said in the past that it is acceptable to stack up to three M200's safely. One of their main concerns for larger stacks is weight - M200's are heavier than they look, and the weight being carried by the bottom amp in a stack adds up fast as you add amps. Some people have stacked as many as four successfully, but I'd try to keep the stacks down to three. If you had five, I'd set them up on two separate shelves.

As for the triggers, Scott had this to say in an older thread :

Thanks gong.
By "rackmounting" I would intend that all weight is carried by the rack-rails. By this I mean, of course EIA rack rails with appropriate spacing, each RU (rack unit) being 1.75 inches. So if I would get 5 M200's the weight should all be on the rails, and whatever the cabinet is that holds them. Thanks for the liks to the threads.
I just might go with three and use my Crown DC300A-series II for the surounds. One more switch to hit, but that's OK. The wife learned how with my other setup.