New power cords for Vintage amps

I have a McIntosh 2105 (solid state) that had the original captive skinny lamp cord type power cord. I had an authorized Mac tech put in an IEC, and then I attached a Pangea AC9 SE cord.
The amp gained authority in the bass region, and also seemed more quiet, although that never seemed to be a problem. I think that it is worthwhile.

I removed the captured power cord from a vintage Harman Kardon amp and installed an IEC socket. I also removed the original 18 gauge cable that ran from the throughout the amp up to the power transformer and replaced it with 14 gauge wire. It was a fun project, but I won't say I heard a difference.
If you can do it yourself, I say go for it. If you're going to pay a couple hundred dollars...that's a different question.

These amps have the original captive power cords and they're approaching 60 years. Not crazy about playing with electricity.

Any changes to classic amp's may or may not improve the sound, but they will reduce there value for sure.

Any really good cord will improve your amp try Stealth or Purist.