Maggies a waste if only 3' from backwall?

I have 3.6's (tried 20.1's) and they are 40" from my rear wall, and they perform very well. I would worry more about what you plan to drive them with,(don't get me wrong, placement is very important, try experimenting with different configurations). They will reward good choices when it comes to amps. 20.1's were amazing, but my 8' ceiling seemed to take away some of their magic and my incorrect equipment choice (and cables) left me wanting more. Also consider bi-amping the maggies to get rid of their x-over, that was a big step forward for my system. Hope this is helpful.

I have 1.6QRs in a 14 x 19 x 8 room with plush carpeting over hardwood floors and drywall walls. I've had to deaden the walls behind the speakers, especially the corners, to remediate excessive brightness and address slap echo. My speakers are out 5' from the back wall which is necessary for getting response down to 40hz. I also use Mye stands, which enables me to tilt the speakers forward to allow the tweeters to align in a perpendicular to my ears at my seated height. To me, getting the vertical right is much more important than the lateral sweet spot. Given the difficulty in getting them set up properly in my room, I've decided against going up to the 3.6Rs unless I can arrange an extended audition in my room. I expect the 3.6R's will be an even greater challenge in your case. I would worry that you will find the 3.6's too bright and I'm pretty sure you won't get nearly what they are capable of in the bass. You might have more luck with the 1.6's or new 1.7s. Also, they are not all that heavy even with the Myes so you could move them out for listening and back again I suppose if you placement concern is appearance driven. If you really need to go lower it might be easier to get a sub to work than the larger maggies.

Given the difficulty in getting them set up properly in my room, I've decided against going up to the 3.6Rs unless I can arrange an extended audition in my room.

That says it all in my experience. Unless you are getting a pair used and don't mind reselling them if they don't meet your expectations, an extended audition is required. I demoed a pair from a dealer for a week before deciding I could not find that "Maggie magic" I hear about.

I would just buy them and give them ago. Really many many brands of speakers should be placed more than 3 feet off the back wall.....

I demoed the 3.6s and 20.1s a few weeks ago in a 14X20X10 foot room with Mcintosh. I thought the sweet spot on the 3.6s and 20.1 was average. It was MUCH wider than Martin Logan's Summit/Spire. But no worse than some box speakers out there such as B&Ws that always put my head in a vise. Off-axis was much better than I expected but not great. I walked around the room to test I heard no hot spots, bass nodes, and the vocals remained clear. The image was not near as sharp as the sweet spot but it was not totally gone either. All of these things will be set up critical of corse.

Some long time uses might be able to give you an idea of how many feet (or inches) wide the sweet spot will be in a room your size.

Best of luck,
James.

Your room dimensions are a little small for the largest Maggies and what do you plan to power them with? Maggies are known to be power hungry especially the 20.1 needing a very powerful high quality amplifier like the Audio Research Reference 600 for them to sound properly. On the other had, basements make excellent listening rooms with their concrete walls and floors. Good luck.