EDIT - new paragraph --- sorry, I forgot a very important news item --- I replaced the 6N1P driver tube with a cryo'd 1960s NOS RCA 6BQ7a, after receiving the OK from Donald that this tube matched his design parameters and pin assignments. No adapter needed. And the effect was stunning and marvelous - the music became much more clear, actually a step improvement in clarity, a big step. In fact, it now sounds 99% as clear and transparent as my modded Sonnet (in which I installed solid silver Dueland signal wires), which I felt on direct comparison is just as clear as the Apex Pinnacle. And the very special emotional presence of the Stratus remains. This tube cost me $25, and together with the NOS 5U4G and 2A3s, it made the Stratus a top-of-the-line amplifier. And that is why ... [end of edit]
I have switched over now completely for instrumental music -- the Stratus with NOS tubes is simply outstanding driving my T1 on a DHC RSC cable.
Last night I enjoyed listening to Brahms 3rd Symphony with Claudio Abbado on DG - this time it was clearly a moving, stupendous performance --- crystal clear, noise-free, each section (voice) in its own location within a big soundstage, powerful (the timpani and pizzicato on the double bass were tuneful, controlled, and visceral), and the strings were liquid with incredible timbre and real resin. I could just hear someone breathe occasionally (quite close on the right in the cello or bass section), which I have never heard before on this recording, and, for the first time, I could hear the small timbral differences and place the different violin clusters in that fast fugal section in the first movement - extraordinary!!
A truly wonderful headphone rig!
So I took the plunge and ordered the Emission Labs tubes - rectifier and 2A3 pair, all meshplate, $862.83 from George at tubeusa (and a deep breath). Hard to believe this will make it even better, but I will let you know.
(I will be happy to be rid of the smidgen of gas discharge in the right 1960s NOS RCA 2A3 that remains even after >100hrs.)