There is certainly a lot of misunderstanding about audio output power by many that have been bamboozled by all the marketing claims and myths. I've been involved with vintage hi-fi equipment for many years and have had many different amps and receivers to play with, the largest being a Pioneer SX-1980 receiver that specs at 270wpc at rated distortion (very low) into 8 ohms. I think that unit has +/- 90vdc rails.
Many of the units have average responding watt meters and I can tell you that the majority of my listening to vintage rock and roll is at around the 2-5 watts output, and that is loud enough for the wife to ***** from the bedroom. The main advantge of having more wattage is the extra headroom responds to audio peaks with a lot less distortion then lesser wattage amps. It's mostly marketing hype and I would state that a good clean low distortion amp that maxes out at an honest 50wpc is more then enough for 95% of the home applications.
Lefty