Too Much Power

All that extra power to prevent clipping is only useful if there are recordings that have a suitably wide dynamic range.  Absent such a large range, the average level would have to be incredibly high for that reserve to ever come into play on the peaks.  Even with notoriously inefficient and difficult to drive speakers, I would NEVER want the amp to actually deliver anything close to 900 or 1200 watts.  I cannot think of any amp over 100 watts that I thought compared favorably with low-powered amps when playing the vast majority of speakers at sensible power levels.  

Aside from greater potential to blow up speakers accidentally, excess power in-and-of-itself is not a problem.  But, in the real world, how one gets there—running many output devices in parallel— could reduce sound quality.  Many years ago, I heard a demonstration of two Rowland amps that were very similar in build, one rated at 50 watts, the other something like 200 watts, running power hungry Magneplanar speakers; I preferred the 50 watt amp, particularly at lower volume levels where the big boys sounded lifeless.  One manufacturer of high end gear touted how his amp used only two output transistors per channel, that is, until market demand compelled him to make an ultra high-powered amp.

I run high efficiency speakers, and with my speakers, the very best sound I’ve heard comes from low-powered tube amps.  One of my amps is an Audio Note Kageki (parallel SET 2a3 rated at 6.5 watts/channel), the other (my favorite) is a custom-built pushpull amp running 349 output tubes (5.5 watts/channel).  I also liked, in my setup, a First Watt J-2 solid state amp that is low powered.  Perhaps I do compromise sound at higher volume levels, but I rarely play my system at high volume levels, and even when I do do, the average output would still be below one watt, and I choose not to compromise that watt with amplifiers that don’t sound as good.

I’ve seen more speakers blown from accidents, like pulling an interconnect with the amp on, or volume set at full blast than the supposed danger of harmonic distortion from clipping burning out tweeters.  That sort of extreme distortion is so obvious that no half intelligent person would allow such abuse to go on long enough for the tweeters to go.  Unnecessary reserves of power do not protect your speakers—they only tempt one to over drive the speakers.

You most certainly can blow a speaker from applying excess power; it is not always the case that tweeters are the drivers to blow because clipping introduces high frequency harmonics.  I wish people would be cautious around their high-powered amps.  The most surprising thing that I've seen is speakers where none of the drivers were damaged by extremely high power being sent through the speaker, but, the crossover failed from the excess heat; that heat was enough to completely melt the plastic bobbin of an inductor which left a lump of wire sitting in a pool of plastic.