Mondial designs (now of Klipsch). Adam Gershon on email, Paul Rosenberg on the phone - offered and delivered free custom work on the output stage of my Act3 to better mate to my Klipsch La Scalas, and were patient and voluminous (and correct!) with help on questions on other units. Professional, courteous, and totally stand-behind-ish. They deserve highest marks.
What companies have gone above and beyond?
I have had a few products back to the manufacturer for different reasons. Some companies have been fantastic to deal with while others have been a disappointment. Sota was so good I couldn't believe it. Aragon was almost as good. What companies have you dealt with that provided exceptional service?