Ferrites can certainly be effective in blocking RF. But so can capacitors which short RF energy to ground. Place them on incoming lines and anywhere rectification of the RF signal could be occurring. Both methods can be used in stubborn cases.
I have seen articles on antennas that use resistors have a lower noise floor . The Tilted Terminated Folded Dipole is one such antenna. This antenna was long used by the military and government entities.
The RFI is generated by —and is radiated from— the screen itself.
You would have to put the plasma TV inside a Faraday cage to eliminate your RFI. This is why plasma TVs are no longer being made. (Having said that, there was at least one brand of plasma TV (Panasonic?) that was not a prolific RFI generator.)
A plasma set, unlike a LCD, requires relatively ...