As for parts quality effecting sound, that's a non trivial topic. I suggest looking at some books written by engineers on amp design. Like Douglas Self. They bust a lot of myths originating from audiohiles not versed in the technical details of amplifiers.
Busting myths is/are the job of engineers. That being said, compare, say a good tube set up to nearly ANY SS set up- same speaker, same sources, same room and the tubes will win- matter of fact Magnepan and MAC did blind testing just as I describe and prove this to be be true. So much for engineer's and their idea of what sounds good. That is akin to believing everything that is advertised on paper is factual- simply not true, yet we are told this is truth, but is it really
true? Ask any experienced EE, and they will tell you - go for the tubes (usually).
I appreciate your write up, I really do, it's an interesting topic. However, what simply amazes me is how so many esoteric designers gain so much regard, and yet pro audio gear is some how of lesser quality? Hardly- not even close to the truth. As if an RCA sounds better then an XLR- no way- no matter the distance. Balanced vrs unbalanced- what is the goal of quality audio reproduction? It should be- Balance. Tonality, Timbre and Pace-recreate what was originally intended by the artist, this is what matters for quality audio- but now I feel am ranting. (lest I mention how a recording was mastered to begin with- another topic altogther)
For example, ATI builds amplifiers for many different vendors- including, but not limited to: Outlaw, Sonance, ATI (in house designs) and many others.
Bryston, originally pro audio gear, does this also, yet a 3B/4B ST (same as several Lexicon's amps) have higher review points and the Lexicon's used price bring way less money- yet same amplifier. AB International - pro audio gear, is Cinepro (very highly regarded and very expensive), Great amplifiers I might add. And the list goes on and on.
It's all about advertising hype and what is preferable on a given day- not really factual engineering designs that are equally comparable. Oddly, tubes- good ones, they always sound good, yes, better then their SS counter parts- no matter how they are compared (when compared using the same source's). But they can be a pain to live with, are expensive (now a days) and create a lot of heat- so- SS is a better option for many users. John Curl for example-designs for what? 5 different brands does he design for, heck maybe even more- do any of these sound better or worse then each other; I am sure they do, but again it's build quality (money allowing for higher quality parts ect.) vrs the hype- IMHO. AT a certain point WPC is simply WPC- this is where the pre-amp and source components are so very important.
By way of example, I had one of Halcron's newer digital amps and it was horrible $6700.00 amplifier and it was simply terrible, loud, ok, so what, so is my Harley. But did this amplifier sound better then what I have- not even close- subjective, granted, as is all of audio from a given point of view, but at what point does money stop buying better sound? This is my real point I am trying to get at.
It is so perplexing for most perspective buyers that they have nothing to really use as a point of reference. A paradox for the buyer, and the engineers wonder why high end audio is dying a slow death? Yet, for me, after trial and error, when one desires perfect audio, that this is when you finally realize- perfect audio is not possible, close ..yes, perfect, no way- no matter how much you spend- nothing beats that of live of "you are there", or listening to the actual studio recordings.
Just my 2 cents worth.