I've been trying various power and IEC plugs when I get the chance. Sometimes customers request a particular set of plugs, for example Oyaide or Furutech, to be put onto their power cords.
Our 'normal' plugs are Chinese "OEM" plugs, which are very good value for the performance. However I was expecting great things from some of the more expensive plugs, ones costing $150 each or more.
But although there was a difference, I did not think it to be a very large difference. Also it was hard to say which one I preferred. Some of this was due to an 'oranges to apples' comparison, for instance, out normal plugs are copper or brass. And I was testing against plugs made from bronze with exotic coatings (beryllium, etc..). And often I prefer the more musical sound of plain copper over plated conductors.
However, just recently a customer ordered a power cord with a SonarQuest Rhodium/Carbon plug set (actually a European Schuko and IEC). This very fancy looking combo is very nicely made with a solid metal body and Rhodium plated conductors. I don't know if the carbon helps the sound or is just for show. But they look very cool.
And to my surprise, these things sound very good - sit up and pay attention good. About the first time I've heard our standard plugs be humiliated like this. I was impressed enough to order some for myself. And I've added it as an option on our NEO and NEO-OCC power cords - it costs an extra $160 for SonarQuest Carbon Rhodium power plug and IEC plug. Highly recommended if you want to push the envelope.