I know what you mean. Your question is specific to ARC, isn't it? ARC states that they have a record of each and every unit that they have ever produced and match the tubes specifically for that unit by pulling the specific records. I do not know whether it is a marketing ploy, however, ARC does some pretty intense testing and quality control from what I am told. I just do not know if it is worth the huge difference in price. I am also very interested in hearing others thoughts.
Tubes & Audio Research Corp.
When Audio Research ships a set of tubes, they have them individually marked to match a certain area where they want you to install them. As long as they are the same type of tube does it make a difference which tube goes where? Are you better off buying replalcement tubes through Audio Research and pay 3 times the normal price for them for the testing they do?