Mainstream Phono Stages Incorporating Premium Branded PCB Parts - Do They Exist?

I did not come to any conclusion. I was speculating. Sorry to have offended you. Glad you’re happy.

I extend my sincere thanks to everyone who replied.  The myriad (and scope) of responses reflect a keen interest in the topic.  As a result, I'm better informed and acknowledge my naïveté regarding audio equipment design, product manufacturing, and quality control initiatives impacting signal quality.  The cost/benefit analysis and technical knowledge required to be successful in the business is substantial.  I learned much from the discussion.  Much appreciated!   

My Experience had and the one which produced a Phonostage that I was not only happy to support being built, but also extremely satisfied with owning. Took place when I rolled the dice on two components. 

I bought in a Copper Foil Cap' at a value the EE was extremely reluctant to use, and Z Foil Resistors that the EE was reluctant to use because of cost in relation to parts and discard from matching. 

The Copper Cap's produced the smile, usually seen when things liven up.

The addition of the Z Foils produced the Cheshire Cat Grin, that is the sign I am selling my soul to get this one. 

In my case the addition of a Particular Brands Design for a Resistor brought the End Sound to one I was not willing to be without. 

This Phon' has been demo'd to quite a few individuals who have been very vociferous with appraisal given. I would suggest the Subjective Evaluation is more of a Collective Evaluation, where findings are notable. 

Pindac, if you are referring to copper foil in oil capacitors, especially those marketed under the Jansen (sp?) or AN name, I have found them to be unreliable when asked to tolerate voltages that are "high" in a tube circuit, but well within their stated ratings. Thus there is no excuse. I have had two catastrophic failures, and now I don’t use them. In a solid state design, where voltages are much lower and way below the voltage rating, perhaps there is no danger. Otherwise, yes, they sound good.

The Z foil resistors I believe are the same as the TX2575 resistors I mentioned, I think.  I associate them with Vishay and used to call them "nude Vishay" resistors.  Somehow Texas Instruments markets them at least in the US. Historically, I think they are like Vishay S102 resistors which have/had a plastic casing around the resistive element.  Turns out they sound much better "nude". But very expensive.

A local dealer has electronics built for him according to his rough specifications on design and his choice of parts.  From years of experience, he knows what parts he likes in the electronics, but, the process still involves parts swapping to get his idea  of the right sound.  This may or may not involve expensive boutique parts.  I saw a speaker under construction where one week, the crossover contained a very expensive vintage paper in oil cap, but the next week it had been replaced with a modern film cap; I joked that he was cheapening the design, but, he replied that the prospective buyer wanted a different sound that the modern cap would supply and that it wasn't really that cheap a part (it was a $400 per piece capacitor).

This same dealer sold his own proprietary amplifiers.  I was asked to give comments on a particular amp, and I had to frankly state that it was far from his best effort.  He laughed because it was an amp that his customer had sent to an "upgrader" who filled it with expensive Blackgate caps thereby ruining the sound.  The customer was also disappointed with the upgrade and brought it in for the dealer to undo the damage.  This dealer often gets in brand representatives who want him to listen to something that he might carry in his store.  He has correctly identified parts in the electronics from their sonic signature; he can tell when Mundorf caps are in an amp or speaker; he thoroughly hates their sound.  

The right part may be a boutique, expensive thing, or it may be something cheap and common; good designer/builders listen and pick what sounds best.