I have no idea why the AVR-X3400H sounds so good subjectively too, so I know why you are questioning. Again, it could be expectation bias at work, that we don't expect something that simple, and cheap (relatively speaking) can be that good. Don't tell Hetfield, but I think the low street price tag probably is messing with his head too
This thing has received enough praises by AH owners already, for $599 or less street price now, it deserves an owner's thread so that we can start collecting all sorts of flowering words on its sound signature, @ADTG where are you when we need you to start an owner's thread?