Try one of your "other" aftermarket power cords on the Anthem to see/hear if it makes a difference/improvement and then go from there.
You list various cables with your system (use what you have @ hand).
DeKay
Will An Anthem AV Receiver Benefit From An Aftermarket Power Cable
I recently simplified my home theater system by moving from
separates to an Anthem AV receiver. The Anthem is internally
grounded so the stock rubber cable has just two prongs.
So would there be a benefit to getting an aftermarket cable?
In my analog system, I use Cullen or similar priced cables,
I would be in the same price range for the receiver.