@pvmike I owned ML Montis and heard 11A and 13A several times. I would describe the sound as smooth, never in your face. The presentation is pleasant but does not excite nor is it extremely engaging. It’s more about striking the balance and keeping away from potentially crossing over the boundaries. These speakers play it safe
I think going with a good tube preamplifier like the ARC Ref series will definitely be a significant improvement compared to the preamp section of your streamer but I wouldn’t bet on the overall presentation to yank you out of your chair and cause you to start tap dancing. That’s not what the MLs are about. If you want that type of excitement you need dynamic speakers that can do that.
Just my opinion.