Magnepan 3.6R

Is my 12x19 ft dedicated space big enough to accomodate a pair of 3.6R's?
Absolutely !

Since 1977 I have used the IIa, IIIa, and now the 3.6 in rooms about the same
size with excellent results. The speaker "couples" best to the rooms
of that size.

Set the speakers about 4 or 5 ft out from the front wall, and sit about 10 or 11
feet away from them. That gives 3 or 4 feet behind the listener to the rear wall.

Place the speakers one third the width of room from left edge of right speaker to
right wall, one third between, and on third from right edge of left speaker to
left wall.

The 3.6 speakers work best in rooms of that size, and worse in smaller or larger
rooms IMO.
You should be good....similar to a room I used IIIs in...although I did think they'd benefit from a larger space. They sounded great though.
IMHO you are spot on Don. Had 4 prs when I had a room like that. Now that I don't wouldn't even consider them.
As a follow up, I am wondering about the suitability of a McIntosh MC275 to drive them. I ask this knowing the strong preference is for high power solid state. My listening tastes run to jazz,acoustic rock, female vocalists, usually at pretty sedate levels. My current speakers are Merlin vsm's. Any comments welcome
What's wrong with your Merlins? There must be an upgrade to keep them sounding better than 3.6s. Just wondering.