How do amplifiers work?

I am looking to gain a better understanding of how amplifiers draw power(wattage), and then send the appropriate amount to the speakers.

I have received different opinions regarding this from several techs. Without getting too techinical, as I am not a technician, can anyone shed some light as to how this all works?

Example: Lets say you have a 300wpc amp, with power hungry speakers(say 87db). You are playing music at a moderately high volume (11:00 on your dial, or -20db). Since the music is filled with peaks and valleys, hi's and lows, how many watts could the amp be drawing during any given post, or peak in the music? Does the draw actually exceed the rms 300 watts instantaniously during a peak. Is this what dynamic headroom is for. Is this where distortion or clipping comes in?

When the wattage or signal is then sent to your speakers, is this the maximum amount of wattage availble at any given time, given the volume setting, with the speakers reacting accordingly? Can an amp sense the power required for any given speaker?

Why do some audiophiles say that 100 clean watts is plenty, where others will say 300 to 400watts is needed to drive the same speaker. Is this because the clean 100watts has plenty of head room? Isn't a speaker capable of reaching its best dynamic heights, with an amp that has wattage to spare?

Thanks, Just Curious