GL problems can be a nightmare that's for sure. Many use cheater plugs or filters as a quick fix. Not a good idea. Find the source or sources.

For you HT types, your cable tv input could be the source.

All my equipment use balanced ins and outs . I make my own interconnects using Canare bi-wire cable and drop pin 1 at the input of each amp or signal processor (called telescoping interconnects). This is a common practice in recording studio wiring schematics.

Make sure the whole system is plugged into the same power source (outlet). A 20-30 amp dedicated line is great.

If you use balanced lines and do the above your system will be dead silent (depending on the quality of your components).