New expensive power cord for amp and no change in sound?

The improvements are all in your head . You spend a lot and expect a lot. Power is    power. In M.O. any decent manufacturer of good equipment would consider a minimal investment in power cords good business. This would be easy and inexpensive way to improve their sound quality. While I've seen sound improvements in speaker and interconnect wires without spending Ks. I don't believe a heavier power cable would make much of a difference. Look more to overloaded outlets change 15amp to 20amp circuit breakers Of course this is Only M.O.

I find that you only hear a difference in power cords if you really think you will.

Maybe you could just fill in the blank as it suits you?

"I find that you only hear a difference in _______  if you really think you will."

Imagine power supply that works like this. You charge big battery from mains, disconnect it and then use to power your amp with clean DC, disconnected from mains. No noise from electrical lines.

So ideal power supply should work exactly like this, rejecting noise and interference. Amp schematics and parts placement may be more or less sensitive to what comes from the AC mains.

Different amps have different designs and different power supplies. Thus some are more sensitive to power cables and some less. Perhaps yours is in the “less” category.

@roxy1927 power cord change from original one one of respectful manufacturers, shouldn't make any listenable difference, assuming original cable is healthy. Many used separates are sold with random, no-one knows, power cords, and in that case, replacing it makes sense.