Magnepan 3.7's versus 20.1's?

Ordering 3.7's Monday,trading 1.7's. I have auditioned 20.1's they are great but too large for my listening room and not in my budget. I also heard rumor that the 20.7 will be out shortly.

the 20.7's are coming. the 3.7's are way more cohesive than the 20.1's.

20.7 is now official:

http://www.avguide.com/blog/first-listen-magnepan-s-new-flagship-207-loudspeaker

Assuming a 'shoe-box' shape, What is the smallest room dimensions in which the 20.1's and 3.7's will work well?

Stickman,
I have 3.7's in a room that is 15.5' x 19.' The speakers are along the short wall, about 6' out from the front wall. Tweeters to the inside. What is surprising to me is that the 3.7's integrate with the room much better than the 1.6's did. I'm actually considering removing some of my room treatments. Because of the size of the speakers, I can't get more than 48" from inside edge to inside edge. My guess is that 15' is likely to be close to the minimum width for the 3.7's. I have no experience with the 20.1's