Power cord supplied with Luxman L-509X Integrated Amp

You are warranting that the manufacturer used inferior cable in their own product. Would you also replace all internal wiring?

Not only wiring, but each and every component they use. With a few exceptions, manufacturers use mediocre components and wiring. Thats Economics 101

Wiring is difficult to change and wiring changes really shine at longer lengths than typical lengths of hookup wire. Internal speaker wire I always upgrade. I have, and will continue to upgrade all signal carrying cabling/wire in my amps were possible. That is a mod that I generally do last, and only if fairly easy/convenient. Not possible on PC boards of course.

An improvement in sound quality would have to be entirely subjective

In theory all sound is subjective right? However, after swapping out component for more than 20 years there is no if or buts, swapping out to higher quality components in key areas does 100% improve sound.

BTW The toaster and microwave was tongue in cheek and I stated their sound didn’t improve. The day I start listening to my toaster I need to be carted off to a home for the infirm.

Can power cords make a significant difference? Yes, but only if the capacitance is different from a standard or regulated power cable, like hospital grade. Otherwise, your gear is poorly designed.

I’ve used quality power cables on Krell, Pass Labs, Parasound, Vac, Audio Note, Cary, Canary, etc. etc. Too many to remember. There has not been a single case ever when a good power cord, not a $100 piece of junk bought on Amazon, has not made a dramatic and noticeable improvement over the OEM cord on any transport, CD player, DVD player, DAC, pre amp, power amp or integrated amp I have tried it.

Thousands of other audiophiles have experienced the same.

Not putting a nice power cord in your very nice Integrated amp is a crime. You are leaving a lot on the table to extract the best performance from it.

Do NOT listen to the usual naysayers like Jason Bourne here. They always post on anything, and everything making no difference. You don’t have to believe me on this, just check their posts / history. It’s all negative posting 100%. That’s their hobby 

I guess the moniker JasonBourne09 was taken by somebody else, so this Jason decided to append his IQ instead of his birth year to his moniker.