New expensive power cord for amp and no change in sound?

Cable advice.

1. Make sure it is proper length.

2. Make sure it is flexible, unless you are into elephant trunks.

3. Shielding is a good idea.

4. Read the marketing. Gobbly gook pufferry, run away.

5. Buy commensurate with the cost of your system.

6. Keep expectations modest.

7. Read forums with large grains of salt.

8. Don't fret with a lack of significant improvement.  Just admire your purchase; your friends surely will.

9. Don't post cable threads. 

Got my head buzzing this morning:

It could be that the $500 cable you mention may not be the best premium PC in its price class for YOUR system. Try others, with return privileges? If you have the ability to audition and return, you might try the price category above just for grins. It might just produce a permanent one?

Or, it could be that your amp, in your system, in your household wiring, in your electrical grid, at the time of day you are listening is not producing anything NOTE-worthy? Punt?

We read the term "expensive" on this forum from time to time. As a general statement, a very-good-excellent audio system will be "expensive." Well selected associated items will also be "expensive" in the course definition of monies spent. But, not "expensive" related to the overall cost of the system and the sonic (or other) benefits received IF "well selected." Divorces are expensive. Paying out of pocket for laser prostate surgery is expensive.

When a PC is included in the box when you break the seal and open it, I suppose a $15 PC "upgrade" would be expensive by comparison?

I felt my X250.8 and XA160.8 Mono Blocks sounded better with Cerious Matrix power cords than the included ones...I do find that power cords are more unpredictable than other cables and cords...Pass does include good power cord, and I use them in secondary systems...though Pass has a reputation for not recommending upscale cords and cables, many articles say they use expensive Silent Source cables and cords in their listening rooms and in shows...in an interview, Nelson Pass said he very much liked a pair of speaker cables that Ray Kimber loaned him, until he found out they were $54,000 a pair...

Two years ago I bought a Less Loss power cord and filter which was about $1800. I put it on my equipment (one piece at a time). Pass Int 60; Innuos Zenith MK 3; Ayre  QB 9 Twenty. Don’t remember if I put it on the PhoenixUSB or not. The only discernible sq difference was on the DAC and it was significant. I’m not a reviewer with good adjectives but, I the clarity and bass seemed better and worth the price paid.

You're one of the few who are not dealing with expectation bias and realize there is no objective difference between power cables and I applaud you.