@andy_wonderwall no worries, and sharing some of the same, probably should have mentioned I run custom made hybrid electrostatic speakers on dual mono tube amps myself. 6ohm, 93db sensitivity would seem easy to drive. Not as much as I hoped with prior attempts using lower power parallel single ended amps in strapped triode mode. Back and forth I went with higher powered tube and revisiting some capable SS amps to find the best match. Your Atma 60 amps and your 4B3 amps are both on my bucket list. I can imagine your 4B3 amp lights those MLs up. When I put a good SS amp on my hybrid ES speakers, it does open a larger door and deeper room into what a capable electrostatic speaker can do.
If I had your Atma 60s I’d be fast on the hunt for a good matching speaker just to be able to truly appreciate and hear those fantastic tube amps. Your 4B3 solid state would be a nice match for my own speakers, and have kept that on my favs list to acquire as a future keeper amp. Lucky challenges to have, you have great taste, happy listening to both :)