As an engineer, I have to say the main issue with power output specs include at least the following:
1) "power" is not the best term to use for audio amplifiers designed to drive loudspeakers to begin with.
2) Loudspeakers need voltage and current to produce sound but as we all know they are not resistors so the "power" they consumed is not the same as the "power" an amplifier consumed, or drawn from the outlet/electricity grid.
3) Even that 66 lbs monster super receiver Marantz 2600 would only be 400W into a 4 Ohm resistor.
4) Stopping using the vague, misleading, confusing term "continuous", instead specify the duration in seconds, minutes and hour that the ratings are based on at say room temperature (or something like 25 deg C) assuming the unit is ventilated according the the manufacturer's recommendations.
Again using the Marantz super receiver as example, it passed the 1/3 full output, 1 hour preconditioning test but I am almost 100% sure it will not pass a full power 1 hour test so the "continuous" rating is misleading at best.
The way amplifier outputs and loudspeaker's power ratings of all sorts, such as "recommended 25-100 W, power handling 400 W, maximum power 400 W etc., kind of rating are not very useful (useful to an extent) for the consumer to size the amplifier they can afford. I think Dennis Murphy would agree with me on this.
I think at some point, people have to not stop assuming that most consumers are not technical enough to tell the difference, and start doing something better, more meaningful, and eventually useful for most consumers.
Examples:
Instead using "power", start specify in terms of output voltage and current such as:
Maximum output voltage............50 Vrms, 15 A for 30 seconds, 5 A for 1 hour (Dyn: 25 A, 20 ms), 2 Ch driven
Maximum output current........... .30 Vrms, 18 A for 30 seconds, 5.5 A for 1 hour
That way, we don't have to worry much about the phase angle and impedance. It also avoided the incorrect term W rms, aka rms power. In the beginning, people is going to want to relate such specs to power, but they can be educated to get a rough reference number by using the power formula in the simplified form, that is:
Power (W) = Voltage X Current, and that would be the so called power W) into a resistor load.
It can be, and likely should be, stated in more detail, but this is just my momentary brain spark right at this moment.