A number of posts by several people in the recent part of this thread, while being well expressed, seem to be using the word "cables" in a loose manner that leaves me wondering if we are still discussing the original question, which relates specifically to power cords.
The reason I raise that point is that from a technical standpoint I would find it far more plausible that in the case of analog interconnects and speaker cables some PARTIAL degree of correlation may exist between using one brand and the likelihood of optimal results, than in the case of power cords.
Analog interconnects and speaker cables have the job of conducting an analog signal from point A to point B. In so doing, their sonic effects reflect the net result of interactions between their parameters and the impedance and other characteristics of what they are connecting, as well as their own intrinsic effects. While the magnitude and significance of that net result can be expected to vary considerably as a function of what is being connected, it seems plausible that its general character will have a reasonable degree of consistency.
In the case of power cords, on the other hand, the relation between the effects of a given cord on the AC it is conducting and the sound that is heard is, literally and figuratively, vastly more circuitous. I repeat my earlier contention that I see no reasonable plausibility in the expectation that given power cord characteristics will result in effects on the sound that are consistent across components that perform different functions, that have vastly different fluctuations in their power draw, that have vastly different amounts of power draw, that generate different amounts of rfi, that can be presumed to have different rfi sensitivity, that interpose completely different power supply designs between the AC and the signal path, and that may be completely different designs in just about every other respect.
Putting it all another way, a finding that choosing interconnects and speaker cables from the same manufacturer tends to correlate with optimal sonic results IMO would say nothing about the likelihood that the same will hold true in the case of power cords.
Regards,
-- Al