The fact is electrostats prefer voltage amps (tube) not current amps (transistor). That speaker needs only 40-50Wrms maximum. Anything higher than that, and you're looking for trouble. I would also suggest having your Quads updated to include the clamp circuit. I do believe they are available. An ARC D70 MKII would work perfectly. Even an updated Dynaco ST70 would be sufficient. BTW the reason the Quad 405 needed the clamping circuit was because it would routinely damage Quad 57's and 63's because it delivered too much current. Even an early Quad tube amp or the commemorative version would work well and I believe that's only 25-30Wrms.
