Thanks again for everyone’s thoughts.
Sadly I don’t think I’m ever going to be in the position to be buying into the Naim Pre/Power hierarchy, so it really comes down to me figuring out if the SuperUniti is working as it should - a comparison with a new Atom in a different environment should make that clear.
And, beyond that, whether a switch to an ND5 XS2 / Nait XS3 or a Nova would be an improvement or just a sideways move. That will be a case of arranging, ideally, a home demo once we are freer to do such things.
It was very interesting to hear of at least some people who have suffered from inconsistent performance from their SuperUnitis. I do suspect that our house isn’t brilliantly wired, and if the SU is particularly sensitive to ‘dirty’ mains, then that might be something to do with the issues I’m having. Again, it will be useful to take it to a separate environment (someone else’s house) and seeing how it performs there.
In answer to the suggestion that perhaps I just don’t like the Naim sound… Well, yes, it’s possible. But the best system I ever heard was a Sondek / Naim / Isobarik set up at Gulliford Hifi in Exeter in the mid 1980s. I thought it was astonishingly good.