Very interesting discussions, guys! Bryon, I think you do misunderstand my position after all. Basically, I do not believe that "neutrality" can possibly exist at all, whether we are talking about a single piece of equipment, the entire system as per your definition, or in live music; and, as Kijanki says, I seriously doubt anyone would think it a virtue if it did. I am not trying to make the perfect the enemy of the good - I don't believe there is a perfect.
Some other thoughts - Bryon wrote "The success of room correction relies on the technology involved and how it is implemented." This completely ignores the human ears setting up and/or listening to the result of the technology (not to mention the designer of the technology). The dealer who set up one room correction system I heard clearly thought he had done everything correctly, and he thought the result sounded just fine, yet the result sounded awful to most he played it for, worse than before the correction. I have heard others that made a huge positive difference.
As far as Bryon's characteristics of a good playback system vs. characteristics of good musical playback, I completely agree that these are not the same thing. Every playback system is different, and two completely different systems can both result in good musical playback. This seems obvious. Where we differ is I don't think either has anything to do with "neutrality."
Bryon wrote "A neutral room will make it easier to achieve a neutral system." There is no such thing as a neutral room. As I said in a previous post, the closest thing might be a recording studio. But the purpose of recording studios is NOT to make things somehow "neutral." In fact, as I said before, it is for the exact opposite purpose - removing as many characteristics of the room noise as possible allows the sound engineer as much leeway as possible to create the sound that he wants - to create the sound color of the engineer's personal choice. This also goes along with what I said before about designers of audio equipment - they are not striving for some sort of "neutrality." They are aiming at their personal ideal of what the sound should be.
Bryon wrote "It seems to me that the value of an audiophile developing expert perception of the playback of recorded music is self-evident." Again, I don't think there is any disagreement here. The disagreement is over whether "neutrality" has anything to do with it.
The bottom line here (going back to the OP) is that many of us feel that just because you change one piece of equipment in the system, making 1) individual pieces of music sound more unique, and 2) your music collection sound more diverse, this does not mean you have operationalized the term neutrality. It just means you have a better sounding system.
Let me give you an example, again going back to the OP. Assume a room with good qualities for music playback, and assume a very high quality music playback system (which this room is of course part of). Now, let us say you replace very high quality preamp A with very high quality preamp B, keeping everything else the same. How will you know which one is more "neutral"? I submit that you can't. But you can know which one makes the system sound better to you. And I would also guess that 100 audiophiles that listened to this comparison would probably split close to 50/50 on which one did sound better, and that there would be many different reasons why each made his choice. This is what Kijanki is driving at when he says "how do you know how it is supposed to sound?" There is no one answer to this question, which is where I think your "neutrality" concept/operationalization falls apart, despite your VERY good arguments - it requires that there is ultimately one answer. But thankfully, there is no black and white in music or music playback.