New Power Cable on a 1990 Hafler DH120?

The sound of an electronic component starts with its power supply. NOT with the wire connecting it to the AC outlet. If you believe otherwise then I recommend joining the Flat Earth Society.

The FES has chapters all around the globe.

Except for Australia…
https://www.theflatearthsociety.org/forum/index.php?topic=63521.0

Have fun. Cord will certainly cost more and do less.

 

Some think zero, others disagree.

Certainly the other mods you suggest would make real differences.
Including the outlet.

Compared to the cord, they are useful things.