To address your point on the limits of human hearing, I think my best input would be my observation that from my perspective there seems to be an extreme variation in the limits of hearing on an individual-by-individual basis. If one person can perceive a sound differential and another cannot, then the first will always sense a gap between his hearing and he others. If some people can also hear what the first hears and some cannot, then the first can say there is a large variation in what his peers are able to perceive. However, the person who cannot hear the difference, or who hears it only slightly, or who can only perceive it when pointed out, they will not think that there is much of a difference. They will see it as something that only one person, or a few people say they perceive, but that doesn't seem to exist.
I am that first man. I definitely hear many minute differences between things in the acoustic world, the analog world, and the digital world. Some people I know are like me but quite few. Most people say they can't hear things that make me sick. Some people can't feel the utter joy of great music when it comes on. I get it. But for me, the only wish I have is that I had more money to keep trying more expensive solutions because I still hear the difference and it is so good to me.
If I am crazy, I'm fine to be crazy. But I don't think I am. I think when Amir gets the higher end Denafrips products he will have great things to say as well.