I too can understand your desire to consider the Magnepans as they are a wonderfully musical and awesome value speaker. I too owned the 3.3/3.5's for 6 years and it was mighty tough to let go of their strengths. They are perfectly suited for music-based systems in moderately sized rooms, but ultimately their lack of dynamics makes them not an ideal choice for HT setups in any sized rooms.....forget about it in the room you describe. The series 20 will not be any different here.
I will comment however that all planars are not created equal and perhaps the SoundLabs might be a viable choice if you are seeking the strengths of such a speaker. There is a new model, nearly 9' tall, that is supposedly even more efficient than the latest versions of the other SL models. As an owner of the A1s, there is not an issue of covering the low end at all. In an HT based system, you will have any number of subwoofers so no speakers need to cover the bottom octave anyway but the SL's cover this area like the Magnepans can not match at all.
Speaker issues aside, I recall that A'gon member Mike Lavigne did quite a writeup on the efforts to build a big room, electrical circuits, acoustical treatments, etc. I would think he could steer you in the right direction in many key areas.
I will comment however that all planars are not created equal and perhaps the SoundLabs might be a viable choice if you are seeking the strengths of such a speaker. There is a new model, nearly 9' tall, that is supposedly even more efficient than the latest versions of the other SL models. As an owner of the A1s, there is not an issue of covering the low end at all. In an HT based system, you will have any number of subwoofers so no speakers need to cover the bottom octave anyway but the SL's cover this area like the Magnepans can not match at all.
Speaker issues aside, I recall that A'gon member Mike Lavigne did quite a writeup on the efforts to build a big room, electrical circuits, acoustical treatments, etc. I would think he could steer you in the right direction in many key areas.