How do I choose a phono preamp?

With a 15K budget, I would allocate about 10-11K for table & cart, 3-5K for phono stage, 1K for cleaning records. With 10-11K for a TT (with ~8/3K split between table and cart), there are lots of options. I would figure out what kind of preferences you have:

- look: traditional DJ (Technics), something with wood (LP12-ish), more of a skeleton design Rega/VPI?

- Are you into 78s? Yes/No

- Do you want option for second tone arm, say for mono cart?

- Do you want anything automatic? Say arm return at end of record? Or fully manual?

- Any preference for direct drive (Technics) vs. belt (pretty much everything else)?

Once you have answered those questions, it will narrow down the field substantially, make it more approachable. 

The PAVCR manual method for cleaning an LP will get a Cleaning finish that can only be described a purified for much much less than $1K.

Neil does supply a per LP costing that I can't recollect, but it is ball park $00.02c per LP.

I use this cleaning method today above all options available to me. 

I expect that you will enjoy the vinyl with the Martin Logans.  Not much bass extension but listening to strings on them goes to a level hard to replicate with other types of speakers.

One of my three systems uses the CLS and I gravitate to it when I want ti listen to strings!

Maybe out of budget but a used VPI HW40 would be a great end game turntable+tonearm. 

Manual Cleaning Methodology is to be found in the Link

https://thevinylpress.com/app/uploads/2024/03/PACVR_3rd-Ed-Ch1_2024-03.pdf

As for a Phonostage, the one in the Link might prove to be ideal for your purpose.

I become aware of this design by chance, and when investigating it, come to learn owners of some of the Branded Designs and models that were much more expensive Phon's, had selected the Digna Model to supersede them in use. This as a selection of discovered reports got my attention 

My own model of the Digna, when having been Tube Rolled created such a good impression, it was out on long-term loans within my HiFi Group for a quite extended period and a few of these guys don't take prisoners.

My own model of the Digna is one that goes to the grave with me.

https://www.kleinanzeigen.de/s-anzeige/digna-ii-c-mr-nixie-phonovorverstaerker/3226853845-172-1764