I am surprised, (pleasantly, of course), that I turned up here in response to my Google request to find out a particular naming application using the word "exceptional". I have learnt a few things regarding the finer definitions and subtle variations of the many words that have been suggested so far.
For what it is worth, it has brought to mind an example of something I remember from long ago when I first started working in an AM Broadcast Radio Station as a Sound Engineer, having been a Radio Mechanic Apprentice before that. This was at the time, about the early 1960s, Stereo Broadcasting was being tried in Australia, but in general well before the FM service started. I had complained that the "LARGE" mono control room monitor sounded "ordinary". It just seemed to be nothing special, but did not have any obvious faults either. It did have power, without distortion, though, as could be expected from the 9 cubic foot enclosure, a triangular corner type from Wharfdale, mounted over the main control desk abutting the ceiling, facing down at a 45 degree angle, right above my supervisor. This sand-filled panel housing for a powerful 3-way system, with its 15" bass, was considered "exceptional" at the time, but I had not recognised that fact, only its no-nonsense ability to do the job required, without adding any qualities of its own to the sound it was reproducing.
I realised later that that exceptional sound was not screaming out "listen to me", but just doing its job well. It did not have screeching high frequencies that made violins sound "steely", or the "thump, thump, thump" of the bass doubling and over resonating. It was effortlessly reproducing the signal fed to it and it was effortless to listen to. It was exceptional sound, at least at the time.
Now, I listen to sound that is better, and reproduced by speakers that are much smaller, cost less in real terms, though one can go overboard here and pay thousands more for questionable improvements, it is a perceived art and that means, what appeals to one may not appeal to another.
I have not been able to add another word to the list, but I hope I have added a real concept awareness to reality as I experienced it. To me, the closest word is "epiphany", as that was the feeling when I realised what had happened. It was actually an "eye-opener", or should that be "ear-opener"?