Why would you think, even for a second, that an AC mains cable - unless badly designed/implemented or damaged - would make the slightest bit of difference on a power amplifier? Do you see pro and live music setups using uber expensive "audiophile" cables? Because the only possible justification would be that an ordinary cable isn't sufficient for the relatively low V/I requirements of amplifiers, and that just isn't the case.Now we knew power cord didn't make any difference to the DAC which has better noise isolation than an amp.
How about some tests on pre-amps or amps? I did hear some differences on the amp using different power cords.