The power recommendation given by the manufacturer is just a rough guide of the kind of amplifier that should be used with the speaker. Those numbers do not necessarily mean that the speaker is capable of operating at sustained levels as high as the top wattage rating. The top end number is probably chosen to limit the possibility of damage even from short term events, such as a loud accidental pop, and I highly doubt that a speaker like the LS50 can take 100 watts for anything but the shortest period of time. I would not want to put too powerful an amp on a speaker for fear that some event might cause such accidental large transients that could damage the speaker even though I would never actually try to run the speaker anywhere near the full output of the amp.
While it is most common to damage speakers with sustained levels of high output (overheating the voice coil), one can also damage speakers with very strong short-term transients. I recently spoke with someone who damaged a tweeter by playing a classical recording that had extremely wide dynamic range (I have a few of these, and they come with a warning about the dynamic range), while not playing them at a very high average volume.
As to the idea that one is more likely to damage a tweeter with an underpowered amp driven into clipping than by excessive clean power from a too powerful amp, I spoke with a manufacturer who said that, by far, there are more instances of damage from use of too powerful amps than from clipping underpowered amps.
I would personally stick with amps more toward the lower end of the recommended power range because I don't do that much loud listening and I find that lower-powered amps tend to sound better than higher powered amps, provided that the speakers are suitable for the lower-powered gear.
