Is there such a thing as too much power?

     Forty years ago, When I "downgraded" from a Phase Linear 400 to a 100 wpc Audire, it was a major improvement, with subsequent improvements since, pretty much unrelated to power.     However!  The best home system I ever heard was a pair of actual B&W Nautilus speakers, which require a highly damped 350 wpc amp for each if its eight drivers.  It was exactly powerful enough.  This owner used Mark Levinson, back in the day.  B&W had their Classe division make amps for these still extant. special order speakers.  I wish Audire could power them, assuming Julius (Siksnius) could still create his magic, plus he preferred 100 wpc amps and speakers that could use them.  It is not all about power.

As far as the car analogy goes, My 350 hp supercharged S2000, is far less tractable, due to requiring 7000-9000 engine speed, than are most turbo cars, such as my 15 psi 280 hp MR2.  This autocross suspended MR2 and most Porsches are great without attracting attention with a 9200 rpm amplifier terrorizing the neighbors.

I like cars...let's go back to the car analogy.

A Porsche GT2 sold to a person that is legal on the street has to be de-tuned to race.  However, horsepower isn't breaking or handling and a high horsepower car without a good breaking and suspension system is limited to being fast in a straight line or in other words drag racing.

A Miata with the right driver can challenge many high horsepower cars because its light weight and balance. 

Not all amplifiers have the same circuitry and components and may not excel in reproducing all types of music...they could be great at a tornado warning not music.

I recently upgraded from a 70 W tube amp to a 500 W solid-state. No comparison, more watts are better. In my opinion ,flea watt amps are interesting and can sound amazing with horns or point source whizzers, but for the large  majority of speakers more power is Better.

The SPL of your speakers are important. Much of the time, under normal listening volumes, you may be using only 1-2 watts. The quality of the wattage, not the overall power, dictates listening happiness. Unless you have big lawn parties with huge inefficient speakers 300 watts is overkill.