Not enough power what does it sound like?

Driving a pair of Focal 1007Bes with a Rega Maia rated at 80W the speakers emmited a loud clicking rattle when I cranked them up too far, with the same amp into Thiel CS1.6s a sustained forte passage in Rattle and the Berlin Phil made the sound seem to sparkle and jump out at me from the sound stage, presumable when the power supply ran out of current (the Thiels were 3Ohn at areound 5KHz), A Naim 250, also 80W had no trouble with the same passage at even higher levels on the Thiels but it had a much stiffer power supply. The quoted power isn't the whole story.

+1 shadorne got it right with a minimum of words.
In addition, if a solid state amp is used, your tweeter may be at risk. A classic symptom of an underpowered system employing a solid state amplifier is fried tweeters.

Clipping is the key word, under powered source feeding the speakers, bad bad bad.

It sounds like s... !

It took a lot of power to drive the bottom end of my known-to-be-hard-to-drive B&W N801's.  That was the biggest difference I can say was for-sure related to power output as I experimented with a Crown XLS-2502 which has tons of power.  It had other issues.  Switching ("permanently") to my Levinson 333 made all of the difference.