I did neglect to address your other Q’s in your OP, but I’d say that your original instincts are correct about that if all the other AC ancillaries (power cords, fuses, power supplies, IEC inlets, duplexes, etc) are fair game for ’getting it right’, then why not on/off switches? I concur. Might throw in fuse holders too, really. In fact I’d say that ALL switches, connectors, fuses, breakers, et al, are The Spawn of Satan in the audio world. The best sounding connector or switch, ideally, is none at all...hardwired bypass will always sound better. But, what can we say, there’s no practical way to live with a "hardwired bypass" condition on everything - totally impractical, impracticable, and definitely downright dangerous! So they are evil - but, a necessary evil, so we accept them and what they can do for us in the real world.
As for an amp power switch, most of the time, from a purely operational standpoint anyway, we might consider for a moment that a power switch for the usual hifi amp may not even be necessary. We could, if the amp is not in a rack or cabinet, just plug and unplug the power cord, presumably, for amps that are not to be left on anyway.
But, in practice, this can be a little dicey sometimes. Unplugging or plugging in too slowly or awkwardly can exaggerate the arcing at the contact points and the arcing may be enough in some circumstances to blow that expensive designer fuse, or perhaps do some kind of damage to the amp, even whether it has some measure of protection or not. Even if no damage to the gear ever occurs, the carbon buildup inside the female AC receptacle will be frequently occurring and impossibly difficult to clean.
And suppose that very rare instance occurs to you one day and your amp suddenly is making a very LOUD and nasty noise and in a second you realize that the power has to be cut immediately or the worst may happen. If the power cord were momentarily inaccessible (as in the rack or cabinet scenario), then the front-panel switch could be a gear saver. An available switch would be the fastest and most reliable way to avoid imminent meltdown. Rare maybe, but in the life of many an audiophile, that day has already come...or is probably going to.
So, for those practical concerns alone, I’d argue that the switch is necessary...and that as long as that’s true, then it might as well be audibly the best kind for the job that is still affordable overall.
As for an amp power switch, most of the time, from a purely operational standpoint anyway, we might consider for a moment that a power switch for the usual hifi amp may not even be necessary. We could, if the amp is not in a rack or cabinet, just plug and unplug the power cord, presumably, for amps that are not to be left on anyway.
But, in practice, this can be a little dicey sometimes. Unplugging or plugging in too slowly or awkwardly can exaggerate the arcing at the contact points and the arcing may be enough in some circumstances to blow that expensive designer fuse, or perhaps do some kind of damage to the amp, even whether it has some measure of protection or not. Even if no damage to the gear ever occurs, the carbon buildup inside the female AC receptacle will be frequently occurring and impossibly difficult to clean.
And suppose that very rare instance occurs to you one day and your amp suddenly is making a very LOUD and nasty noise and in a second you realize that the power has to be cut immediately or the worst may happen. If the power cord were momentarily inaccessible (as in the rack or cabinet scenario), then the front-panel switch could be a gear saver. An available switch would be the fastest and most reliable way to avoid imminent meltdown. Rare maybe, but in the life of many an audiophile, that day has already come...or is probably going to.
So, for those practical concerns alone, I’d argue that the switch is necessary...and that as long as that’s true, then it might as well be audibly the best kind for the job that is still affordable overall.