I have owned both the Montana Kas (375 lbs each speaker) and the Aerial 20T (270 lbs each speaker). Both are excellent speakers, but the big difference is height of
each, the KAS is a tower speaker around 70" and the Aerial 20T is a two-part speaker 48" high. I found the Montana KAS sound reproduction capabilities more suited to a large room setting. KAS'love to be played loud and if one has a fetish for playing music at high decibel levels, then these speakers are wonderful speakers for listening in a large roomy setting. In a small room area, they are too overpowering and your ears will suffer. In comparing the Montana Kas to the Aerial 20T, the difference begins with the factor of size, but if one is seeking a very comfortable pair of speakers, that one can listen to low for quiet music listening on a sofa, then the 20T is a fine choice. The Kas' are not as suited to listening to on
low quiet listening levels. You can but the KAS Speaker thrive when played sonically high. I want to add, however, that the 20T speakers are no slouch if one wants to play music a little loud. Granted their loud sound capabilities are accoustically softer when compared to the loud-playing Montanas. The sound of the 20T is clean, clear and very comfortable to listen to. I did not find them taxing to my ears as the KAS will do over several hours of continuous listening. Knowing what I know of each of these speakers, the 20T or the new version Aerial 20T (Series 2) is more ideally suited for those of us who have a moderate 20x15 room dimension setting. The Montana will suffocate and overpower a small stereo room setting, as I painfully learned the hard way. A tall tower speaker like the KAS breathes and performs best when their sonic power can be spread over a larger room area. Your stereo room size will dictate which speaker will work best
for you.