Marakanetz - The di/dt currents in the power cord are what matters. IF it is too inductive, the drops can be in the Volts, not mVolts. I have one of the lowest inductance cords on the market and it is getting rave reviews when used with power amps. If you read my description on my poer-cord page, it describes how the voltage drops can occur. Poor power cords can have the same effect that plugging into multiple power strips has, except on transients. If your amplifier has switching supply, the impact of a low-inductance power cord may be much less, because of the regulation.
BTW - twisting the two current-carrying wires has the additional benefit of radiating a smaller magnetic field that can impinge on nearby interconnects compared to two parallel wires.
BTW - twisting the two current-carrying wires has the additional benefit of radiating a smaller magnetic field that can impinge on nearby interconnects compared to two parallel wires.