Life After Your Magnepan’s

You certainly have a large room for any Maggie if you like going louder than 90 dB cleanly and forget about bass below 40 Hz with any degree of dignity.
I owned Tympani IIIs back in the mid 80's. I drifted back to Acoustat 2+2's with subwoofers because the detail was better in the midrange and with the subwoofers was a significantly more powerful set up. 
If you wanted the ultimate in a room your size I would do Sound Labs 845's with 6 subwoofers placed equidistant across the front wall. That would give you the ultimate sound stage and cruise effortlessly at 110 db if you were so inclined to destroy your ears. You can add subwoofers to Maggies but the effect is not as dramatic as adding subs to a full range ESL. With Maggies you are only improving the efficiency of the woofer panel. With a full range ESL you are improving the efficiency of the whole thing. 
I love Maggies. In their price range they are hard to beat if you like the presentation of a tall dipole but if you can afford an 8 foot tall ESL and can put up with the size there is no more accurate or detailed loudspeaker. If you match them up correctly with the right subwoofer array yo are in another league altogether. I have listened to Wilson's, Magico's and YG's and they are all great loudspeakers if you forget about the price. But, they can not hold a candle to full range, line source ESLs with subwoofers and considering Sound Labs 9 or 845's are a fraction of the cost it boggles the mind why anyone would by them. 

The one speaker that will truly amaze you is Sanders Sound.
Roger Sanders makes one product in his Colorado shop and
it is shockingly superior to everything else. $17k.
Buyers get a lifetime warranty and a 500 watt stereo Amp.
Read up and watch his videos. He know of what he speaks.
My dogs about freaked out when I demoed them. Oh yes
he uses transmission line bass so you wont feel shorted.

Hello stickman 451,

     Are you sure you really want to move on from your Magnepan 20.7s?  I believe you'll likely regret it for numerous reasons that will likely become painfully obvious once you switch to any other speaker options anywhere near their price point.  Yes your room is large at 21.5'x30' but given your high quality system and speaker components, I suggest you explore methods of optimizing your current system prior to seriously considering making any possibly unnecessary and costly changes.
     I'm basing my opinion on you already owning all the required excellent component parts to achieve near state of the art full range sound quality performance in your room and my personal experience achieving similar full range results with less expensive system component parts and in a smaller 16'x23' room. I utilize Magnepan 3.7i main speakers in combination with a 4-sub distributed bass array (DBA) system very similar to the Audio Kinesis Swarm system reviewed by The Absolute Sound in the link below:

https://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/

     I can attest to this review being a very accurate description of the very high quality bass and seamless bass integration with your 20.7 main speakers you can expect, even in your larger room.  Because you already own a pair of very high quality REL G-2 subs, however, I know you have other options for attaining excellent supplemental bass performance in your room.
     If you're mainly concerned with performance results at a single dedicated listening seat, I believe you can do so by just optimally positioning your two G-2 subs and 20.7 main speakers separately in relation to your listening seat.  I could describe exactly how to do this or you could request your local REL and/or Magnepan dealer come to your home and do it for you.  
     If you prefer great bass results throughout your entire room, I'm as certain as I can be that you can do so by either utilizing the 4-sub AK Swarm DBA system or creating your own custom 4-sub DBA system. This could take the form of adding two more G-2 subs and optimally positioning and configuring them. But I believe it could also take the form of adding two more smaller REL subs, such as the 7i or 9i units, and achieve very similar results. 
     Another option is the 6-sub distributed line array bass system suggested earlier by mijostyn, either with your 20.7s or his suggested Sound Labs 845s.  I agree with him that having 6 subs lined up along your front wall is the ultimate bass system in terms of volume and dynamics, however, you or your domestic partner may not accept the room décor statement of 6 subs lined up along your living or family room wall.  But if you have the freedom, I think it's the only bass system that could equal the 4-sub DBA's bass quality and exceed its bass SPL levels.
     As to your thread topic, though,  Magnepans have been my favorite choice for main speakers but, if I had to pick others, I'd probably either choose Sound Labs, Tidal, Vivid or Magico.

Best wishes,
     Tim

audiokinesis2 I think your reply describes the Maggie situation very nicely.  I bought the LRS and they sound better with 500 watts Bryston 4BSST vs. the older Muse 150 monoblocks that put out 250 watts both at 4 ohms.  Actually the tube preamp really made them work with the Muse but I use the Bryston BP20 with the 4B.  Anyway moving them upstairs into a space that I can make the back reflection really "work" and amplify the bass at the same time, it's amazing.  Bass not as deep as with the two REL T5i used with the Muse, but sound overall is more stage like and coherent with the Bryston.  I have them facing windows covered by a light filmy curtain which is a plus to block out some light and provide privacy, but also mainly really disperses the sound well.  I put a thick curtain in front of them to minimize first reflection.  They really do well although ultimately don't go deep enough for my tastes or hit you in the gut but as to filling that huge room it's pretty darn impressive.  For 715 bucks to my door I like them. 

Hello gammonit_2000,

     I agree completely, the LRS are excellent and might be the biggest audio bargain in decades.
I’ve used four different models of Magnepans in my systems during the past forty years and I had the best results with high powered solid state class AB and D amps, it seems like the higher the better and I’m currently using a pair of 1,200 watt class D monos. On another thread here, however, a member said he was driving his new pair of LRS with a 40 watt VTA tube amp with very good results, which really surprised me.
     I don’t think there’s any doubt that the Magnepan’s dipole operation contributes to their open and airy sound quality but I don’t think it contributes much to the bass performance. The last two pairs of Magnepans I’ve owned, the 2.7QR and 3.7i, have had excellent bass quality (fast, detailed, natural and seamlessly integrated) but only have bass extension down to about 35 Hz, which results in a lack of bass impact, heft and realistic, natural sounding bass dynamics.
     The Audio Kinesis 4-sub DBA not only provided excellent bass quality (fast, smooth, detailed, natural and seamlessly integrated) on both Magnepan models but also provided bass impact, heft, realistic and natural sounding bass dynamics along with bass extension down to 20 Hz +/- 3db.
     Since the Magnepan LRS only have bass extension rated down to 50 Hz, I’m certain their overall performance would be greatly enhanced with the addition of, ideally, the $3K AK 4-sub DBA Swarm system but also significantly enhanced with the addition of virtually any pair of good quality subs one prefers.
     I realize that some prefer not to use subs but I also realize that sometimes we just don’t know what we don’t know, or even dare to try.
     Total price of a pair of LRS with an AK 4-sub Swarm DBA would be about $3,700, with two good quality subs it could total only about $1,900. With either available with 30 day in-home free trial periods, there’s a big upside with really no downside with both except a bit of time.

Enjoy,
Tim