Using tube amp with electrostatic speakers.

Ralph was too modest to claim it, but he is a high level expert on tube electronics and electrostatic speakers. I would trust him implicitly.

Furthermore, I have run a pair of his 'circlotron' tube amplifiers, Atma-Sphere M60's, into the ESL panels of ML speakers. They sounded very good indeed.

jimbreit - I have some experience with your question . I also posed the same question a few years ago . Only a few people responded with less than great advice . Most stated a couple hundred Audio Research watts would be needed with my stats (King Sound). I pretty much was convinced i would never have a pair of tube monoblocks in my system due to the economics involved and focused on ss . 
Fast forward to last year . I picked up a Primaluna Dialogue 2 integrated rated at 35 wattts . At the time i had 6 pairs of boxed speakers that the plan was to use the primaluna with . One day i decided to put it in the main system with my King Sound stats and was pretty impressed with what i was hearing. Zero distortion as the volume increased to very high db's . I was able to play the primaluna just as loud as the solid state .
I have never purchased a amplifier unheard but plan on getting a Primaluna Dialogue premium hp some day . I can only imagine having the extra 35 watts over the dialogue2 will sound like .

My main point would be don't get hung up on the watts of a tube amplifier and research the current it can provide . 

Without the ZERO’s Ralph’s amps sound poor with 80% of the speakers out in the world!

How many people use Zero’s anyway?

And those that do not, do just fine IMO!

There are lots of tube amps that will sound fine on ML speakers without Zero’s.

Most speakers have "roller coaster" impedance curves, and do just fine with most all tube and SS amps.

Do not buy into this "theoretical nit picking" impedance BS.

That does not matter much in the "real world" listening experience!