Fred, I quickly(too quickly)read the article and punched some of my typical numbers(3 meter listening distance, 89dB speaker sensitivity, 80dB average listening level, 20dB headroom above that to allow for an occasional peak on the most dynamic recordings)into the calculator. The result came up 113 watts, which was clearly far too high as I had in the past measured and calculated the power usage as about 32 watts in that 100dB peak situation. So, I read the article a little more closely to see what was wrong and saw that the factor they used in their distance formula was simply 20xlog(D2/Dref), and applying that indicated that what the calculator was doing with distance was reducing the sound level 6dB for every doubling of the distance. This is correct for an omnidirectional sound source operating either in an anechoic chamber or out of doors where room reflections don't reinforce the sound level, but a complete analysis in a typical listening room requires that this be taken into account, and makes a major difference.
Curiously, the article makes this rather basic point clear only near the end under "Other Considerations", where it's stated that the calculations apply only to anechoic or outdoor environments and suggests that a 6dB correction(i.e., reducing the power required to 1/4th of the previous result)be employed to account for the listening room. Following this suggestion, I used 14dB rather than 20dB of headroom in the calculator, and sure enough the result was 28 watts, much more closely in agreement with the 32 watt figure that I'd calculated.
So, without the room correction the calculator doesn't "work just fine for the rest of us", but gives power requirements about four times too high. Hopefully the fact that Crown deals in very high powered professional amplifiers wasn't a factor here.
