I am a bit unsure where we have got to with this thread.
I think that we have established that:
The Mutec clock will work and that as it auto switches according to incoming file resolution the Bartok’s need for two separate wordclock inputs will not be a problem in practice.
That your Naim Uniti Core should work flawlessly with Bartok. Alternatively you could use Roon but as you don’t stream that is of no interest to you.
The only thing that i do not understand was your comment that :
Of course the Bartok will upsample to DSD ( or DXD) from PCM files fed to it from your Core. The only main difference is that Bartok will do it better as the algorithms for upsampling have been refined since the first generation and the processing is faster.
One thing that you certainly will find different to the Classic series is that the 3rd generation is far easier to use than the Classic stack. It is also controlled by an app ( Mosaic) on your phone or tablet unless you want to pay extra for the universal remote. When you use the app you will see that as well as control, the streaming of local files and providing access to streaming services ( subject to subscription) it also provides internet radio. For me in the UK that is important as it allows access to the HD version of BBC Radio 3 which has the best audio quality.
If you are to buy a Bartok I would say that it would be a shame not to use the streaming services facility. I too am old and have thousands of hard copy discs, silver and black. Of those there are hundreds that I do not play. Why? Because I had to buy them to hear them. All I had to go on for the purchase was a hunch or a review. Many turned out to be just hear once and file away for ever. Now with streaming I can listen to almost all of the new releases that interest me before committing to a purchase.
Of course Bartok cannot play those CDs and SACDs that you have . So you will have to keep your Verdi although, frankly, I would not rely on its longevity unless used very infrequently as its Sony transport mechanism does not have a great reputation for reliability ( I went through 3 of them, or rather three OPUs, while I owned a Verdi, so that’s approx one every three years) and spares are generally NLA. That is on the open market. Perhaps dCS could comment on whether or not they still have stocks. However sooner or later you will have a big choice to make regarding those optical discs. I just did for my collection by buying a Rossini Transport.
In any case why not just accept streaming? Owning lots of one type of thing does not stop you enjoying another. BTW with Qobuz you get a lot of the full data too as for many albums you can read the full CD booklets online. Even Mosaic app can show information including the artists, composer(s), producer, engineer , date of recording etc. subject to the raw information provided by the record label. I think that you will find streaming enhances, not diminishes, your musical life.