I hope this might be useful for those wondering about the merits of these three models, as I had, and whether to upgrade. Three years ago, I bought the Naim Uniti Star and PMCtwenty23s. Suddenly I’d found the kind of sound I had been looking for over the years. On the strength of that I bought, as a second system at a different location, the Atom and PMCtwenty21s. I was delighted with both.
I have recently traded in the Atom and bought the Nova. The Nova now plays with the 23s and the Star with the 21s. For what it is worth, this is what I found: the Star produced a marked improvement in sound from the 21s. They became different speakers to my ears. They love being tickled by the Star. Similarly, the 23s sound better with the Nova: broader, bigger, happier and much improved bass.
I realise this kind of story comes around often, and that views are subjective. My only purpose here is to report my impressions (and without the nuanced language the more expert amongst you employ – and which is very useful. It’s just that I am not fluent in it).
I’m left feeling really delighted with the change. What went before was certainly good. This combination works better for me. BTW, I found Cultured Audio in Hanborough, Oxfordshire, and could not have found better advice and encouragement. They set up in 2021 and are worth visiting.