Help Me Narrow My Choices

I recommend Zesto, Audio Research, or Conrad Johnson. The highest level... used, best way to go in this category. I have owned Audio Research for my Phone amp for over thirty years. Each time I upgraded I always did a complete search and evaluation of the category and always chose Audio Research Corp. The improvement was always absolutely huge until I got beyond the PH8. Still very substantial after that... but more refinements after as opposed to complete change and improvement. 

I have heard a few of the $4K priced units, but I found a Parasound JC3+ and have never looked back.

In the past ten years, I have been a user of an MM Phonostage design as a Valve Input / Valve Output > SUT (own two SUT's). On occasion, the SUT's are replaced with a few designs of a Head Amp. In the same time period, I have used a Phon', ' that is a MC/MM Valve Hybrid Design that has been used as an MC Input compared to the MM Input > SUT's and Head Amp.

Very recently, I have returned to using a Solid State MC/MM Phonostage, which has been experienced as an MC Input and a MM Input > SUT's. 

I can't offer guidance on how these compare to other Brands of Phonostages being suggested. I can say the Full Valve and Valve Hybrid Phonostages have been extensively compared to Phonostages where the purchase cost was ascending up to £10K and I was not left with the notion they were bettered, recollection is that the owned Phon's were very good competitors and not bettered.

The Full Valve and Hybrid Phonostages are being compared to the new SS Phonostage, and again, neither is the absolute betterment, but each does have something to offer where the end sound produced is very much wanted to be lived with.

Talking about the impression the end sound makes on an individual is not describable in writing or words. It must be the individual being exposed to the end sound that is the information that allows them to describe the impression made and to accurately evaluate the impact on them.

All Phonostages owned are the result of many years of expressing an unusual interest in Phonostages and having achieved many demonstrations of different designs of Phon's. Has been an enabler for my being confident in knowing what I want to be wed to and discovering the designs that fit. Which, in use, are extremely satisfactory for my purposes.

I strongly suggest allocating some of the $4K budget being referred to for supporting making arrangements to experience Phon's of interest in use. Demonstrations are such a worthwhile experience to have.  

For SS, Parasound jc3+ or Lehmann Decade Jubilee are excellent performers at their price point from long term established companies with great reputations.

For tube phono, it might depend on the OP’s preference for warmth vs neutral, and how low/quiet the noise floor.