Where to put your best power cable?

put it on the power distribution unit and buy cables that are OCC single Crystal copper which is the best wire for audio proven now for over 50 years.

I'm inclined to say power amp too but you need to try both ways.

Your results will vary depending on your components, the AC within your area, and your home wiring. I wish one answer would be correct but as you can see from the above comments results vary and you should experiment to see what works best in your situation.

I use mine for the power amp, direct into dedicated 20A line

Trying it is the only way to know.