Here's how you can find out. Conduct a level matched, double blind level listening test, with various content, preferably music and see if you can tell the difference. Only one anecdote but I did just that with what ended up being a Marantz SR6013 vs an Onkyo NR686 (I was blinded in the usual sense as well as to the two receiver models themselves). I was unable to hear a difference when in their respective direct modes, which is where something like Marantz's HDAM should seemingly be in play.
