I own NAT se2se amps and do have not a problem driving my Soundlab Ultimate II speakers. I think they are using the GM70 tube now but I have the older model with the 211 tube. Getting everything synergistically working together will pay great dividends. I can assure you the NAT se2se amps WILL be more than what you need to get your electrostatic speakers to sing. Hopefully this is not your first excursion into tubes but having preamp, cables, power cords, placement of your speakers will reap great rewards. I know thats pretty much the standard response around here but it took patience and a little frustration to get my system to where its at currently as far as sound goes. No more merry-go-round for me. I have no dealer or no affiliation with NAT products. Just my.02 cents. Hope it works out for you but patience and synergy is the "KEY".
Hope this helps
Chuckie