What was the first power cable that you noticed a difference in the sound?

@carlsbad2  I find your first suggestion very interesting.  If I understand you correctly,  there are amp designs that manage power in such a way as to make power cables a non issue, assuming of course you are using any decent cables that can carry the required current in the first place.  My last three amps have all been Hegel products.  H390 to the H590 and currently a pair of H30s.  I have heard zero difference it sound regardless of the PC I've tried.  Was using Furutech DPS-4.1 and currently using Puritan Ultimate.  Throw the stock cable that Hegel supplied into the mix and the sound is the same.  Will I hear an improvement if I spend thousands on the PC?  

Power cables don’t really make a huge difference with an amp. Components like Streamers, is where p/c upgrade is noticeable.

nordost  Heimdall works  for  me 

The only really noticeable change for me was, an Isotech power cord to my Modwright power supply.

Shunyata Venom-X EF

With patience these can be found used for $500