Why the last few feets of cable counts? Because the powersupply "sees" the ac through these last few feets of wire. It is like a blood.vein, the atreia that feeds the powersupply.
And as we know; the quality of the powersupply defines the quality of a component.
About romex; the only way to avoid any quality-loss of the electric signal is to use single solid-core conductors of sufficient gauge. Most "experts" undercalculates this value because do not incalculate the dynamic headroom needed here. Same with speakerwires btw.
Me I`ve used a shielded solid core pc`s for decades, after an eye- and mouth-opening experience with the old version of the powercords from Electrocompaniet (8x14awg solid core) vs stock pc`s. And then a simular step up when swapping to diy single core 12awg.
Thye truth is sometimes so simple that most people won`t accept it.
