Quality Power Cord

With a $500 budget, I'd suggest looking for a Vitus Andromeda power cable. Threat cable sounds smooth, natural, and yet resolving. I preferred the Andromeda pc to my previous Acoustic Revive Power Reference pc which itself is a good value cable. Also all Vitus Audio's top components are internally wired with Anromeda wire.

@Runnin

I didn't pay for the stock power cable, it came with the Amp.
I am just guessing that the price for a such a cable would
be $1.00, maybe less.

You may also look at used power cables from famous cable companies on 2000s era which sells under $200. They are really good. Next step could be to change their AC plugs with even Furutech Fi-15 (Gold or Rhodium) which sells new ~$100 (both Male and IEC). You will get the same result coming from Power cords priced >$1500! This comes from my own experience. So recently I even tried for a couple of weeks the High Fidelity Ct-1 Power cord ($2800), which was a disappointment based on its price tag and compared to my own Semi-DIy power cables ($300-$400).

You could send me pm and whether you need more info.

cheers,