Albert, I hope member Cerrot will chime in. He owns the latest rev of Sanders' speakers - the ones w/ the aluminum woofer; i *think* it's the 10D but I'm not sure.
If you look at his system, he's using Sanders' Magtech amps as well.
The electrostatic speaker can be modeled electrically as a huge capacitor which means that it's output impedance is high at low frequencies & low at high frequencies. Just the opposite of any conventional box speaker. So, the amp has to be designed to output sufficient current to drive into a higher load impedance at low frequencies otherwise the bass response will suffer. I believe that Sanders' ESL & Magtech amps are designed to this. There must be other amps in the market that are also designed to drive an ESL but none of them come to mind.
The Wolcotts are not an option any more, I believe, as they are out-of-biz (?).
Maybe Tube Research Labs (TRL)? I know an acquaintance who has successfully used them on his Apogee speakers but the Apogee is a planar magnetic speaker; quite different from an ESL.