As a fellow Elise owner I appreciate your findings, @OctavianH. I just completed a very time consuming endeavor related to my profession, and am a bit behind all of you "high rollers." Still burning in my Tung Sol 7581A'a in the power position driven by Tung Sol 6SN7GTB's, perhaps 100 hours on the 7581A's. Quite a lot to like with this current combo.,, and I also have a pair of NOS Sylvania 1952 6SN7GT's arriving next week. Depending upon the results with those "bad boys" driving the 7581A's, I'll likely order 2 more adapters from Deyan and switch the 7581A's into the driver's seat. I listen to more classical and acoustic music (just a smattering of classic rock) and am still debating if I follow your route with KT66 powers or bypass that step straight to KT88's. Decisions, decisions!
You can wait until next week when more users will have KT88 in place and decide later, based on their feedback, on which way to go.