Great input Mike !!
Did you say that you were using Mosaic's upfront? And if you are did you audition any others for the mains "Clarity's perhaps". Which would be my other choice. And Mike lastly did you consider Montage's as surrounds, or did you need a wall mount speaker?
In addition to the Mosaic and Montage, I auditioned the Clarity's and Aeon i's.
Clarity - nice speaker, but it lacked the immersive sound of the Aeon's (and ESL in general). The extra speaker mounted on the back of the cabinet also seemed to cause reflection off the front wall, bass was a bit lacking. I had demo'd these previously as well, but ended up buying a pair of scenario's instead.
Aeon i - Had money not been a factor, this would've been my choice. The typical immersive sound you'd come to expect from a set of ML's and they disappear when the music starts, low end was acceptable. Only negative: small sound stage, if you're not in the sweet spot, you lose the immersive feeling.
Mosaic - great speaker, good bass. I was expecting to hear a big difference between ATF and ESL and I was pleasently suprised to hear otherwise. If i were to rank these out of the ML products, I'd put them between the scenario(first ML speakers I ever owned!) and the Aeon i. Fairly broad soundstage, immersive and warm are the best way to describe them.
Montage - Of any ML floor speaker, this was the one that really sounded like it didn't belong. The high end seemed muddied, and it just didn't wow me like ML's other products.
I ended up not considering the Montage as a surround because of the muddied high end. I did consider another set of Mosaics though, but I prefer something smaller for rear surrounds and surrounds, and if possible wall or stand mountable. It's much easier to put the Fresco or Vignette at a proper listening height if you're wall mounting rather than having to build a platform for a floor speaker.