williewonka, thanks for all of this good information.
I'm trying to be a minimalist in terms of adding filters and suppression directly to my audio gear. I would rather, if possible, quiet the noisy appliances on those other circuits and keep my audio circuits as unfiltered or nearly unfiltered, so that the AC is delivered as is.
I will be doing the all house solution first and may apply both stage 1 and 2 protection out there. I have two dedicated 20 amp circuits with isolated grounds for my audio gear. Instead, of re-arranging the panel, or adding a separate panel, how would I quiet my AC/Furnace, dryer, refrigerators, etc., from spilling noise over to my audio circuits? What type of units are available to use on those types of appliances? I'm not familiar with that approach.
Kenny