Just wanted to share,
My hunch all along was that the superlative sound I was getting with the Triode Lab SET 2A3 amplifier was based on the synergy between it and the Micro-ZOTL preamplifier. The 2A3 provided the timbres/colors, "meat on the bones" imaging and the ZOTL provided the dynamics/speed and the special spatial dimensions.
I now have tried running the 2A3 with three very good tube based line-stages on the Ulf's and the "magic" was greatly reduced in the areas of PRAT/speed, overall dynamics, and a much flatter sound-stage quality. So, this validates that it's the combo's synergy that gets you the magic I kept reporting.
I'm also coming to the conclusion that the AricAudio SET KT-120, with KT-88's instead of the stock 120's, is a better match for the Ulfberht's then the 2A3 amplifier. Aric's amplifier opens up the sound-staging ability of the Ulf's to a much higher degree and is very close, if not a clone, of the beautiful timbres/tonality of the 2A3 tube sound. Nothing is quiet as "wet" or colorful as the 2A3 sound, however with NOS RCA triple mica black plate 5751's as driver tubes and the JJ KT-88 blue glass tubes the AricAudio SET is not far off in these areas. The match of the Triode Lab/Micro-ZOTL is still my favorite for the DI's that seem to not struggle with this combo in the area of a total open sound-stage and disappearing in that sound-stage.