As I wrote in my blog, if you have any old upstream outlets consider inspecting/replacing them with at least Contractor/Residential outlets. For those of us not lucky enough to have dedicated outlets, there's a lot that could have been done wrong upstream, so it's a good idea to get into those as well.
Eaton Residential / Commercial outlets are cheap, ~ $4 each. My house is 17 years old and I found loose as well as back stabbed outlets which had to go, so I just went through them all in the listening room.