David,
If you try and think logically about this - count the points of contacts from the transformer on your street till the power reaches your transformer in your amplifier, the contact point at the AC outlet on your wall is number 21, that's assuming a dedicated line and no sub panel, all of which has the potential for a less than optimal point of contact. After your power outlet there will be at least 8 points of contact before your transformer is energized.
So while I agree that the quality of the AC outlet is important ie it has to provide
a solid point of contact with as close to zero ohms of contact resistance. If it is a solid connection point then I'd have to state that any perceived difference of sound quality from various AC outlet's is truly in the ear of the beholder.
Having your electrician do a service on your panel for an example, tightening all the connections etc will have far greater impact than the make and model of your quality AC outlet.
Good Listening
Peter