I switched from EH6550 to GL Reissued KT88 several years ago and the GL is SUPERIOR in every way. Surprisely GL is warmer but also much higher resolution.
My amps require 4MQ so NOS is out of the question. Looking for a tube with the sound of GL Reissued KT88 but higher resolution. Willing to give up a touch of body and bloom ... I DON'T want a SS sound. I'm satisfy with GL but like to experiment ... a bonus with tubes.
I try not dealing with Upscale any longer. ~A years ago I emailed Upscale, Goodwin High End and Audiowave on a EquiTech 2Q. Only Alan @Audiowave replied and ended up purchasing 2 new units from him. Thank GOD for the internet ... have found many great dealers.