Don_c55, while your calculations are correct, IMHO, it is not that simple unless you are listening to a 1K test tone @ 3 ft in an anechoic chamber. You must consider other factors like, actual listening distance and dynamic peak SPL for a preferred listening volume. I think the calculator in this link gives a more reasonable answer as to how much power is needed. Very easy to use, just plug in the numbers for an immediate answer.
http://www.allegrosound.com/Power_AllegroSound.html
Listed in Revel's specifications for the F208 is recommended power of 50-350. Obviously, it does seem that the F208 is better suited for higher power, however there is always an exception, as Cal3713 noted. Also, Cal3713's speaker has a 87db sensitivity and recommended minimum power of 100, while it's possible to find another 87db speaker with a recommended minimum of 10. So why? I believe it is due to type of cabinet, motor structures of individual drivers, number of drivers, complexity of crossover, and probably other factors. All of these require varying amounts of power to function at peak performance.
We are all certainly entitled to our own opinions, so considering the music Kartikeyp listed, classic rock, assuming at times, he may "crank it up", can't imagine that for background music, and classical, some having very wide dynamic range, I'm thinking speakers from Zu Audio. I have listened to a couple of Zu's with Threshold Class A, as you know a Pass design, and thought it sounded extremely good, at least to my ears, which from working in the audio industry for over 20 years, have heard many different components, speakers, and combinations. Also, have listened to other Zu's on different electronics, and they always seen to have the "live" musical character, which I prefer, as opposed to what I call a typical "hi-fi" sound.
So to answer the question in a general sense, when matching amp and speaker, I would always rather have a little more power than actually needed, as opposed to just barely enough.