Curious to see if this will help reduce noise.
You might want to look into the Uptone Audio MMK, Mac Mini DC power conversion. I think it is around $135 sans power supply.
Sounds like a solution to the noise problem.
Do you have first hand experience?
I changed mine out with a PS Audio C7 when I caught a great sale on I believe music direct. It did make a difference I could tell when viewing the HDMI through the Anthem into the plasma. Not so much that I could tell in sound quality upgrade. The difference I believe is much more due to it’s connection points into the Mini as well as the outlet as they are much more solid!
The PSA C7 upgrades made a nice visible difference when I connected them into my DirecTv DVRs as well!! Again I believe due to the much more solid and stable connections!
If you have the budget, you might want to consider removing the noisy switch-mode power supply from the Mini and replace it with a linear power supply instead. I did this with Mojo Audio and it made a gigantic difference.
There are some options for me to consider.