Noise coming from subwoofers and centre channel

Not quite sure where you are in your investigation.

If your system is connected to cable tv I will share I had a pretty obvious hum/buzz. 

What solved my problem entirely was connecting the following Jensen VRD-1FF IsoMax CATV Digital RF Isolator between my xfinity coax and the xfinity cable box needed to run my TV.

Jensen Iso-Max VRD-1FF 75 Ohm Inline Digital CATV Isolator Hum Eliminator (parts-express.com)

Note that the coax from outside is first split and one leg goes to the TV and the other to my modem/router.  This was only needed on the coax leg going to the xfinity cable box.

Hi,

No my system is not connected to any TV cable.

Thanks for sharing.

I only use a powerbar...I am happy to have made the discovery but I do not want to put my system and our security at risk....with the cheater plug...

But, your entire system already is at risk as you’ve got no surge protection and there are many here who’ve told tales of losing expensive equipment plugged into the wall.  I have a vey transparent Wiremold power strip, and when I wanted to add power conditioning and surge suppression I just got this and plugged my power strip into it and my whole system was protected on the relative cheap.  I still question if your power strip is plugged in with a 3-prong plug if the cheater plug makes any difference — I don’t know the answer but maybe someone like @erik_squires or someone else does.

https://www.usaudiomart.com/details/650064731-audience-adept-response-ar1p-power-conditioner/

FWIW.

I only use a powerbar...I am happy to have made the discovery but I do not want to put my system and our security at risk....with the cheater plug...

But, your entire system already is at risk as you’ve got no surge protection and there are many here who’ve told tales of losing expensive equipment plugged into the wall. I have a very transparent Wiremold power strip, and when I wanted to add power conditioning and surge protection I just got this and plugged my power strip into it and my whole system was protected on the relative cheap. I still question if your power strip is plugged in with a 3-prong plug if the cheater plug makes any difference — I don’t know the answer but maybe someone like @erik_squires or someone else does.

https://www.usaudiomart.com/details/650064731-audience-adept-response-ar1p-power-conditioner/

I suppose it’s also possible that installing a power conditioner may fix the problem with no cheater plug needed. FWIW.

I’m a huge fan of Furman power conditioners, but I can almost guarantee no conditioner will solve a ground loop problem, no matter how much you spend on it.

Cheater plugs will work, at a high safety risk. What you really want is to isolate the signal ground that causes the loop, not the AC ground.

While there’s nothing in a Furman or megabuck power conditioner that will solve a ground loop, moving all AC plugs to the same strip sometimes is a solution, but it’s not a matter of any circuitry but rather that the grounds are so close.

The OP has already moved everything to the same outlets.  He's pretty much demonstrated that what he needs is an HDMI isolator.