If it’s not bothering you from your closest listening position I wouldn’t worry about it. AFAIK ground loops exist to some degree in all our systems it’s just a matter if it’s loud enough to be a problem.
Based on what you’ve said it sounds like your TV cable my be the worst culprit and it sounds like you’ve already moved to solve it.
I had ground loop problem between my subwoofer and DirectTV antenna that I resolved by routing the antenna coax through my Trip-Lite surge suppressor. Here is a link that might offer some help if not I’m sure someone else will have better advice.
http://www.epanorama.net/documents/groundloop/index.html
