I don't know how to discuss defining hi-end audio beyond my own (and therefore unique) personal experience. So for "you" it's going to undoubtably be something different. but i do know what anyone who loved their stereo system and/or even more significant- their love of music and their passion for sharing it with others really gets to the heart of things. As I met more and more people who invited me in and asked me what I thought of this or that album, it wasn't so much what they had to play it on (everyone had a different budget level and shopped different stores), it was their tremendous enthusiasm that impressed me the most.
Eventually I got to hear better and better stuff, I could definitely relate to the YouTube video of 1950's Hi-Fi (thanks JMGROGAN) and remember browsing in department stores as a young kid looking at console stereo's (with built-in television sets). When separate components came out on display in the 60's i swore i would someday get a nice stereo, too- Fisher, Scott, Marantz, WOW was i excited. One afternoon my dad and I got to hear a demo of Voice of the Theatre speakers! But... they didn't sound much like the real thing to my ears even though you could hear them three blocks away.
Finally in my 30's I graduated from a Denon amp to a Hafler and then spent a "small fortune" and replaced it with a used Levinson.
WOW all over again. Instruments had real texture, and the notes took on a whole new dimension of liveliness. I was finally able to come up with the enormous amount of money it took, and that it was beyond my reach only a few years ago. I had felt guilty, embarrassed, even silly for wanting such esoteric gear just to listen to my CD's. I just know how great the music sounds these days, and just accept how much I enjoy the experience.
So nowadays if people want to know "how many watts" my speakers have, I'll tell them "100 each" and just let it go. But if they really like what they hear, I'll also add that "it's quality not quantity"....