Originally Posted by
Macca
A bizarre thing to say but IME dealers who actually know what they're talking about are pretty thin on the ground. Or they may have some real knowledge but they're still going to make stuff up to get a sale. I'd avoid any dealer who tried to sell me mains-related gadgets including fancy power cables, because they're either one or the other.
Vast majority of amplifiers will not care how 'gritty' the mains supply is. Even the very best mains supply contains horrendous levels of distortion, but since it is converted from AC to DC by the amp's power supply it doesn't matter in the slightest. The only time I've actually heard mains supply affect sound was at a bake-off where at tea-time the voltage dropped so low it caused an SE valve amp to motorboat. The solid state amps were unaffected.