Knowing about music doesn't necessarily mean that someone will know what sounds good, or great. It makes someone listen to the music differently, though. While we, as people who play instruments, may notice an interesting chord progression, rhythm, harmonization or the way the different sections are tied together, we are also paying attention to something other than the actual sounds and details. Saying that you want to be a "Golden-Eared Audiophile" is like saying that you want to be an art, food or wine aficionado- just wanting to be that doesn't make it possible. To know what sounds truly great, you would have to hear it and notice that it's much better than the rest of what's out there and to do this, you would need to listen to the best of the best, to have a reference. That said, without having listened to the best, it's still possible to consider your system to be "great-sounding", but there may not be any level of agreement among other audiophiles.
To consider yourself a "Golden-Eared Audiophile", carries with it a level of snobbery. You will usually find fault in the sound from other peoples' systems, you'll notice how bad the music sounds in a theater, grocery store, mall corridor, concert, music festival or anywhere else you are "subjected to bad sound". When you go to a store that sells audio equipment, you will most likely annoy the sales people by nit-picking and talking about what's there, but shouldn't be and what should be, but isn't. The people at some stores may eat this up but if you go to a store that isn't high-end, you'll be avoided like the plague by the sales staff, once they realize this. Trust me- when people are trying to make a buck, talking about the minute details of a receiver/amp's shortcomings will not win you any friends.
If you have been playing guitar since the age of ten, you have learned to listen to the music and learn songs, licks, chords and other details of the songs (I can't imagine not being able to learn by ear, but many can't). However, if you have played electric guitar for long, you can count on having some hearing damage. If you want to really know what you're hearing and why, have your hearing tested by a real audiologist and tell them why you're having the test. They usually don't go higher than 8K because their purpose it to make it possible for people to hear speech better, not music but if you know that you're more sensitive at 2K in one ear and the other ear's acuity is normal across the band, you'll know why it sounds like the left channel isn't as loud as the right. This will affect how you perceive many sounds (this, from personal experience).
If you list your absolute favorite guitar sounds (not effects), it's usually from the amp and speakers sounding good with a particular kind of guitar. A Marshall with Jensen speakers in an open cabinet is not going to give you the classic Marshall sound. For that, you need Celestion speakers in a closed cabinet. A Fender Bassman or Twin with Celestions on a closed cabinet will not give you the sounds made famous by those amps. That producer was right- get a great basic sound and it'll be easier to manage.
Something many people have never thought of: the music we listen to is an illusion. It's not the way it sounded in the studio, if a studio was even involved at all. Placement of the instruments, ambience, timbre, frequency response of each instrument and the whole- all determined by the engineer and/or producer. A guitar that sounds huge on record may have been recorded with a Strat and a Tweed Champ and no effects (Layla). In a studio, less is always able to sound like more and engineers hate excesses in sound unless they can control it and use it to their advantage.
You posted "Once you've trained your ears for detail, the next important thing is thing is putting it all together.". It requires training the mind, at least as much. Ears don't remember, the mind does. Ears don't think that a little added at 4K makes the soundstage seem wider or that a little more at 8K makes it seem higher. That's called 'psychoacoustics' and it's used in recordings all the time, whether the person mixing/mastering knows why, or not. The mind is at least as involved in our perception of how we hear as our ears. It fills in blank spots in sound and ignores others without us having to even think about it.
If you become obsessed with creating a system that's as close to life as possible, your listening room will have to mirror a studio's control/mixdown room because that's where the decisions were made to make it sound the way it does. They may listen on a small system because they know most people don't have a snowball's chance of hearing it the way they do and in fact, many good producers listen to what they record on a boombox or a factory car stereo. They usually want it to cut through and sound good where people listen most- while they drive or as background. Very little is mixed for "Golden-Eared Audiophiles", using high-end equipment. There is no real standard for a music system, although THX does try to make it possible to hear a movie soundtrack sound as similar in as manyh places as possible.
YMMV
