Great news! You don't need a power conditioner at all and you were wise to give your audio system dedicated 20 amp circuits. The bad news is that you have a grounding problem. That ground rod you said is just for your audio equipment absolutely must not be connected to anything but the houses main ground rod, and only if it is 6 ft or closer to the main grounding rod. If it is more than 6 get from your main ground rod then the most affordable option is to abandon the audio system ground rod. Everything in your house must tie to that one single point the main grounding rod through your electrical panel. From that main ground point you could put in a new ground rod every six feet until you reach your audio ground rod, but I would just abandon the audio ground rod rather than pound in more ground rods around the house just to reach it. Once that audio system ground rod is disconnected and you are connected to the house's grounding system in the power panel you will no longer have the noise problem and you will no longer have a blatant code violation that could be used by your insurance company if there was a fire started by any part of your audio systems electrical wiring or anything plugged into that system.
An Audioquest Niagara 7000 would absolutely fix the noise for whatever you plug into it, but you would still have a code violation that could be used against you if there was a fire and you would still have a grounding problem that could cause noise elsewhere. It would be much cheaper to fix the root cause by hiring an electrician to disconnect your audio system ground rod and verify that you are still connected to the ground in the power panel that feeds those circuits.
Best regards
An Audioquest Niagara 7000 would absolutely fix the noise for whatever you plug into it, but you would still have a code violation that could be used against you if there was a fire and you would still have a grounding problem that could cause noise elsewhere. It would be much cheaper to fix the root cause by hiring an electrician to disconnect your audio system ground rod and verify that you are still connected to the ground in the power panel that feeds those circuits.
Best regards