I think some (most?) amplifiers will have at least some capacitors in them - presumably they need to ensure 'smooth' power supply, so pumping power into capacitors, to then be released, would 'smooth' any small changes in direct power supply.
I think?
My amp is 5000w RMS
but I don't think I've ever run it at that volume - because that would be insane in a house, lol.
Most high output demands in a home setting are very transient - i.e. bass beats in music, a crash in a film, etc.
IIRC the fuses in most houses are 'slow break' so it's possible to exceed their rated power for at least a short time, which is why it should be possible to get monster power for the peak outputs without tripping things out.
If you're playing sine waves at 0dB, of course, all bets are off