Can a power cord increase the resolution of an Class D (SMPS) amp by more than 5% ?

No, unless you want it to...

I’m having trouble seeing how a power cord could make a difference.  After all, the stock cable should be capable of delivering the full mains power available to the amp, and the power supply on the amp is going to clean up any minor amount of interference that could possibly sneak in between the wall and the unit.  

Besides, if it was easy to greatly increase the performance of an Amp with a different power cord, why wouldn’t they just ship it with a different power cord?  Why handicap yourself is there’s such an easy solution?   

tutetibiimperes,

I know and understand why a lot of people feel power cords are just so much "snake oil". If you ever get a chance to try a few, well give it a whirl. Just keep an open mind and listen closely. You might be surprised. Maybe.....

No matter what the voltage is at your outlet, the idea is to get as much of it to your gear as possible, so the age-old counterpoint/argument "what about all the wiring between the power plant and your house?" is moot.
Voltage drop, and the corresponding performance loss that results from it, is real and it’s scientifically measurable. Unfortunately, every power cord suffers from it, but to widely varying degrees - up to a 3% voltage drop is considered "acceptable" in power cord manufacturing.
If your amp is only fed 117 volts, it will not produce the same amount of power/performance as when it is fed 120 volts. Simple.

With that said, you certainly don’t need a power cable costing 4 or 5 figures to combat/minimize voltage drop.
Is there snake oil out there? Of course there is! How else can a company justify a $10,000+ power cord?
However, the mere existence of snake oil does not negate the existence of voltage drop and its effects.

Try some different cables with different gauges and go from there.

Cheers and good luck!

Voltage drop... if it's a concern for you.

Have at it.

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=5.211&voltag...