The for using assymetric gauge came from the idea that can I use power cables as speaker cables. Ignoring the fact that these are heavier and inflexible compared to speaker wires, shielding on these is much better than ordinary wires & gauge is also pretty thick. So if one can use asymmetic gauge then power cables can be very interesting choice for speaker cables.
Jmho, a power cord, cable, would be a bad choice. Especially if the power cord is UL Listed. If UL Listed as a rule the insulation, dielectric, covering the conductors is rubber or PVC... Not good for carrying audio signals.
Also as @oldhvymec pointed out shielding is not a good idea. It can suck the air from the music.
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