I've heard 3.6s but not owned them, they always sounded veiled to me......
I have owned 3.7s for 3 1/2 years......
I will say they need at least half a thousand hours to truly loosen up, and background music won't cut it.....
In my experience, 4' off the back wall is too much, I have found that about 3.25' is perfect in terms of bass balance, but my room is probably different than yours.....
I'm about 18 inches off the side walls.....
My experience has been that tweeters out work best for me....
I aim the tweeters via laser right into my ear lobe at the listening position, and with them on the outside, I get extraordinary realism overall.....
I've owned so many dynamic speakers I've lost count and I am very content with the 3.7s.....I can say the Maggies love lots of juice and I've found the magic amp is the Bryston 28BSST2......but I use a tube pre (Convergent SL1 Renaissance w/ Phono....
I may go to the 30.7's someday, but only if I get a little bit larger room.....I'm pretty happy with what I've got in a 24x16 space
My Magnepans:
https://www.youtube.com/watch?v=BF3wnfIAsQk