"High end" is only indirectly related to quality. The gauge, pure and simple, is money. It's the lofty price range that's limited to the few who can occupy it. Using a normal distribution, we could say that "high-end" is one or more standard deviations above the mean, or about 15% of the head-fi population. This would mean that mid-fiers are in the +/- one SD range, or about 68% of the population. Low-fiers would then make up the group that's one or more SDs below the mean, or about 15%.
Thus, "high end" is relative. If your equipment is in a range that 85% of users can't afford, then it's high end -- regardless of SQ.
Of course, we could be even more discriminating and raise the high-end level to 2 or more SDs above the mean, but that would mean only 2% of the population would qualify, and that might leave the forum high and dry.
It's kinda like IQ. Everyone wants to be a genius. But unlike intelligence, high-end equipment can be bought. And that's a big difference.
BTW, Thermionic, great writing. One of the best I've seen in a long time.