Interesting that we have different perspectives in this hobby. I also could not see how replacing a noise free transistor preamplifier with a tube one could help solving a noise problem, and would never consider such hypothesis for technical reasons, but later found that the LL1.1 measurements show that this tube preamplifier has an weighted noise floor more than 20dB lower than the old version of the NH18! Fortunately you solved it changing wiring and grounding. However, I feel tempted to consider that a LL1.1 would give us more of the characteristics of ML3. As you have opened the Pandora box since a week ago, can I ask if you have tried driving the ML3 directly with MSB Select II?
Our best known politician, when asked once why he changed his mind so frequently had a great answer "Only donkeys never change". I think that this applies particularly well to our high-end systems!