I guess I am lucky to live in a location where power noise issues do not seem to be noticeable, at least in my system. I do understand how power issues may be more noticeable to folks who live in multi-family condominiums or apartments with shared power, and suspect the effect of conditioners might be more noticeable in some of those situations.
In my system, dedicated 20A circuits, 10 awg Romex in the wall, good outlets, shielded power cords of sufficient gauge using noise cancelling geometries and good connectors, and components with well-designed power supplies seem to be sufficient to keep power line noise below what I can perceive. I do power my front-end digital gear from an Isoclean 60A3 II that is mainly used to provide multiple outlets rather than for any conditioning.
In the case of my amplifiers, those are plugged directly into the wall and have no on-board power switches or in-line power fuses. However, in the wall, I have wired two thermal magnetic switches (one per amp) that are exactly as used by the amplifier manufacturer in their most current amplifier designs. Those serve as the on/off power switches and protection for the amplifiers, since they do not have on-board switches or fuses. The power cord length to the amplifiers is 1 meter and I have tried shielded and unshielded power cords with no perceivable difference.
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