Filter caps won’t see a difference if the speaker draws one watt or fifteen watts since the voltage across it is constant from no load to rated power draw. The headroom is in the mains transformer and power transistors.
Do caps stay "fully formed" even under minimal load? (SS)
Theoretical question. If my ss amp can easily handle 120wpc into 8 ohms, but most of the time I'm only using less than 1 watt, will the "unused headroom" (if there is any?) of the power supply caps degrade? Suppose one day I get very hard to drive speakers and all of a sudden I'm pushing 15+ watts. Will the caps be "out of shape"?