Just a couple thoughts. I'm listening to the LTA UltraLinear on the X5's as we speak and it is glorious, nothing clinical about it here, and the sense of intimacy is fantastic. Not a harsh note uttered. I didn't have a 40 Ref to audition, but this one meets my needs just fine in a modest size room. I do agree with you BRM, on the AtmaSphere amps, as I had M60 MKIII's as well. They're definitely not for everyone nor every speaker, but in certain situations (e.g. Duke's) very nice.
I've always had mixed emotions about the extent of break in effects, at least with electronics and cables. That said, I've had the X5's for about 6 weeks now. I try to listen 2-3 hrs every evening, can't really let them play in the background at other times, in our living situation with my wife still working from home in a smaller space. Mine have maybe 100 hours now max. During that time, these speakers have gone through a lot of gyrations, very inconsistent too, like nothing I've ever heard. At first, I thought, "what have I done?", but as you know, I stuck with it. The more they played, they just got better and better, with fewer and fewer sprinkles of despair mixed in. Finally, I refined the placement in the past couple weeks, which cleaned up the mids some more and locked in the image, slightly backed the bass off as well. Now, the combination does everything I want, no downer moments at all. Listening is not a tense technical activity, rather a pleasure every time, very consistent, and most enjoyable.