In recent years, Marantz has attempted to upgrade its equipment and resuscitate its high-end image from the Saul Marantz days.
I would agree with that statement. It appears to me that Marantz is kind of marketing itself as an upper end Denon, ala Lexus to Toyota.
And according to my engineering source, Denon, Marantz, and Sherwood Newcastle all come out of the same factory. That does not mean they use identical circuitry or design.
I agree as well, but they are all more than capable of driving 4 ohm loads across their entire line up which leads me to believe there is more than just the same parent company behind and inside them.