Keith-
Are you placing these filters on non-audio circuits? If you are the first outlet vs. the last outlet on the same circuit doesn't matter, install the filters on the circuit and call it a day, we are making too much out of an easy plug and play install. If I understand correctly you only have one model filter, placement vs. combination is not as critical as some of the other circuits we design with multiple models installed on the same circuit. In your situation I would install the PE in appliance outlets to lower noise. lamps, coffee makers, washers and dryers, window air conditioners, and refrigerators are all good examples.