I have been using a pair of 2805’s for a while. Two generations on from your 63’s. When I talked to Kent from Electrostatic Solutions, he said he has every generation of Quads set up at home and he likes tube gear with all of them.
I may agree, I have both a VAC 70/70 300b push/pull tube amp (65 watts) and a Krell KSA250 amp of many watts... They both sound very good but, the tube gear makes the Quads really open up their sound.
Kent was using an Audio Research Reference 75. The problem with the 30 watt tube amp I am selling was that it just did not quite have enough drive for my 2805’s.
If you could find a reasonable tube integrated, like a Rogue Audio Cronus or Stereo 90 amp, I think you might really like that sound....
Regards, CHRIS