Thinking of Magnepan ... finally!

I had some 3.5R's and loved them.  I found them as power sensitive as a rock.  You are right about the power.  As such, there is a definite improvement with these speakers with as good of speaker cable as you can afford. 

Bass - I ran mine with a sub and found them a bit bass light without.  I believe this is a personal opinion. 

Breathing Room - my room was smaller than what you are running yours in.  You have ample space.  The more you can pull them from the back wall the better.  My sweet spot was about 4' from the back wall. 

Mods - I ran their crossovers and found them good enough for me.  The big improvement I found was with heavier/better speaker cables.  These are power hungry speakers that have to be fed. 

Value - have you considered used?  I believe there is a long waiting list for the LRS.  You might find some 3.6 or 3.7.  Even 3.5's if they are mint.  The large wear piece is the ribbon tweeter, that can be replaced.  The ribbon tweeter can take you places that I don't know that the LRS is able. 

Imaging - once positioned correctly, these can take you to places of audiogasm.  You can close your eyes and they can be very 3-D.  They are very exact and play everything.  You can hear people talking in the background of recordings.  Piano becomes a real audio treat.  Of all the speakers I've had the Maggies went to a whole new level with Dire Straits Love Over Gold. 

I sold these speakers about 10 years ago.  I do miss their sound but moved a different direction about as 180 as it gets.  Maggies play everything and I found this can be fatiguing.  All speakers have a certain sound that they do well.  What I now listen to is, low wattage SET with high efficiency Altec Lansing 16 ohm, VOTT's.  These were true NOS as I bought used, but unassembled  in boxes as they sold in 1959, when the person originally bought them.  The enclosed wire, to link the horn tweeters to the crossover was a very light gauge 3 wire.  While I did upgrade from the factory original, I have found that speaker wires play virtually no roll in driving these.  Very opposite from the Maggies. 

@arafiq Don't confine yourself to Maggies.  Also Check out the SoundLab speakers.  

https://www.soundlabspeakers.com/

As a long time Maggie user, I can say that much of what is said about them, at best, exaggerates their supposed "weaknesses". Your room is probably great for them...you have more than enough power.....if you want them that far out in the room, fine, but that's more than necessary.  And imaging? Anyone who claims that to be a weakness has NO idea what they are talking about. The bass issue depends (as always) on placement and also what you listen to. If you want to rock out, a sub or two is great. (The integration issue is also overblown). There is almost no sidewall interaction with planars, so you can use them to your advatnage regarding bass. If you listen to more acoustic music...acoustic bass on Maggies is absolutely superb. Piano also.

I recently changed my room around such that my Maggies didn't work so great, so I boxed them and put in something else. But I am not selling them because I know I will eventually want them back in the system. As much as I like the MUCH more expensive speakers I am currently using, Maggies make an unforgettable imprint on your brain.

As someone else said, listen for yourself.

Good luck!

@arafiq

despite my often finding @secretguy 's commentary here cynical, spiteful and crass, in this case i agree with everything he is saying about the maggies

as you know, there is much much written here on a-gon about maggies big and small, old and new - i trust you have read through those posts carefully

my short advice is you must try them in your home, as much as share my thoughts here, i would be the first to admit that others’ words cannot convey what these speakers can do, especially when one’s prior reference are speakers such as harbeths fritz's other nice box speakers...

maggies are very very special speakers when given a room environment (and amplification) in which they can shine -- they have a level of beauty, fullness, coherence, wholeness and purity/clarity of sound that is a simply level (or two) above

i would say start with a nice used set of 1.7i, get them on magna riser stands (many used sets are sold with them) outlay is quite reasonable,resale not difficult,  try with and without subs (which i think you already have) - done right current gen maggies do not lack bass... though they don't produce the kind of pistonic woofer midbass in your chest 'punch' that some rock/edm listeners want

... and like pretty much ALL speakers extant, a pair of rels underneath bring them to a significantly higher plane of performance

get the speakers don’t worry about trivia like mods etc etc (those are minor and easy).... you’ve got a good amp for them now, as impassioned as i know you are in this hobby, experiencing maggies is a bucket list thing for you... one which might open a door to a new level of musical pleasure

Room treatment makes or breaks any listening room. 

Audio Research Uses Maggies in the room they use to verify all is well with every item they build. See the youtube video where Michael Fremer takes the tour.

Room treatment will allow you to use Maggies.

My room is treated all four walls and the ceiling.

It sounds fabulous. See my pictures.

Tom