That is because they are old school, they have jumpers.
I am going to kind-of disagree about the "musicality" of NAD. I do listen pretty darn intently and I gotta say I don't notice a difference in SQ between the Denons or NADs (ha, nads

) or the Yamahas, Onkyos, Pioneers and so on.
Now, when pressed to higher volumes (lets say you are listening to same jazz with a good bass line) and you start encroaching on 60 watts per channel or so (probably peaking up to over 100 quite a bit) the NAD may actually sound cleaner. It has the ability to handle 4 ohm loads and probably lower for short periods of time. The Denon can handle it as well, but not with the same amount of control (slight clipping). It always helps to have large reservoir caps and a meatier power supply for that type of listening (music listening mostly)
For movies and moderate level music listening you won't really be able to tell the two apart.