Watts and power

You mean like statements like this that ONLY apply to pure-class-A and make assumptions about heat-sink materials, power supply architecture, etc. that are not a given in all designs.

One pound of weight for every 2 watts is a good litmus test for evaluating Class A amplifiers. An amplifier weighing less might not be pure Class A. It might be almost Class A, or it might be one of the many products which achieve a Class A designation through trick circuitry.

What's funny is that people will quote the likes of Pass when it suits them, but ignore the other things he writes when it suits him, like

Large inductors in series with the transformer primaries and secondaries can be used to stretch the duration of the charge pulse to the power supply capacitors, improving regulation and reducing noise. 

... those large inductors negate heavy gauge power cords.

Of course, not everything that Nelson pass says/rights is entirely accurate either:

Also, it helps if the power supply capacitors before and after the switcher are very substantial. This is typically not the case, since one of the primary motivations to use switchers is to save money.

Power supply capacitors before the switcher are not "substantial", as small values are essential to achieve good power factor and THD, a typical design goal of AC\DC switching supplies. As a matter of fact, substantial capacitance on the front end of an AC\DC switching supply will reduce the requirement for output capacitance to achieve the same performance and will reduce the overall cost to achieve the same performance.

Reading through the posts so far, the answers from @georgehifi read the most correctly to me.

Watts, or power, is equal to voltage multiplied by current. But an individual speaker may want more voltage at some frequencies, versus more current at other frequencies. And if your amplifier is limited in one of those dimensions, it will have trouble driving the speaker.

There are other amplifier considerations for sound quality, but specifically to the question of high power ratings not having drive capability, it's the current and voltage numbers you are looking for.

The SPL calculator referenced earlier assumes a simple speaker load and unlimited current/voltage capability. I use it too, but only as a guide.

Hey there @audiozenology

That dip in impedance is a factor of woofer electro-electromechanical properties and sometimes a 2.5/3.5 way folding in another driver. Crossover may shunt current from woofer to tame a peak.

The speakers in question were a pair I did a complete speaker and crossover analysis. I am confident of my conclusions. The impedance dip was deliberate and unnecessary. A simpler 3 way low pass would have duplicated the transfer function and raised the minimum impedance by 2 ohms.

However, in a lot of cases, your statement above would be true.

Define "read the most correctly". Are you am amplifier design/EE?
If you don't exceed the rated continuous or peak wattage at a given impedance, then you have enough current (and voltage).  Georgehifi is making assumptions about performance that are not supportable with the data on hand ... namely wattage at a given impedance. I won't claim a 1500 watt $500 amplifier is going to have the overall sonic performance of a high end class-A amplifier, even at 100W, but with a speaker that drop to 2 ohms (approx), an amplifier that can deliver 1500 watts at 2 ohms, is not going to sound "anemic" as long as you don't drive it into clipping.

Watts, or power, is equal to voltage multiplied by current. But an individual speaker may want more voltage at some frequencies, versus more current at other frequencies. And if your amplifier is limited in one of those dimensions, it will have trouble driving the speaker.

Oops, sorry meant to say:

simpler 3rd order low pass

Best,
E