A good set of tube amps will be magic with M-Ls. I have an older pair of Sequel II's which do have lower impedance than the more current versions of their ES Hybrids. These speakers and some ReQuests I heard (back in the day that the ReQuests were being sold new) driven by ARC tubes was the best sounding system I had ever heard, for under $20K, save for my friend's $15K Sound Lab A1's driven by Jeff Rowland amps. He and I went to a demo of Boulder amps with a total system cost of well over $100K and it's couldn't touch the quality of full range sound of the electrostatics.
Electrostatics and tubes
I am looking to get some new to me speakers, I've been looking at options and would really like to try a set of planars "electrostatics". I have read or heard somewhere that as far as speakers go they tend to be inefficient (85 to 89) vs.90+(db) on the Klipsch or Dali's I've been tossing around as a standard speaker option. I guess my question is would I need to worry about any over heating issues. I plan on using plenty of power with a set of VTA, M-125's to power them. I am looking at a lower budget set maybe Martin Logan ESL 9's or Magnepan 2.7i . Just wondering I would hate to over heat a few hundred dollars worth of tubes if I don't need to. ¯\_(ツ)_/¯ don't roast me to bad I cry easy 
thanks.