Kal... Using a stereo power amp rated at 600 wpc (and therefore capable of large voltage swing, even continuously) I monitored peak voltage while playing dynamic music as loud, or louder, than I normally would do. With this setup I varied the crossover frequency. For the high frequency signal the voltages which I saw, if maintained continuously, would correspond to power levels far higher than the continuous rms power being delivered.
People who design audio amps for 150 wpc provide power supplies that can maintain voltage corresponding to not much more than 150wpc. In my view it would be better to run a much higher power supply voltage even without ability to maintain it continuously. (This is sometimes called "headroom"). The FTC rule about power specs, and audiophile fixation on the FTC power spec, discourages such a design approach.
People who design audio amps for 150 wpc provide power supplies that can maintain voltage corresponding to not much more than 150wpc. In my view it would be better to run a much higher power supply voltage even without ability to maintain it continuously. (This is sometimes called "headroom"). The FTC rule about power specs, and audiophile fixation on the FTC power spec, discourages such a design approach.