Your observations are not dissimilar to mine years ago. Had a well regarded 200wpc hybrid power amp driving my Magnepan 1.7's. Swapped that our for a Marantz PM 8005 and could not believe how much more natural, smooth, warmer and more musical things sounded!
Been a Marantz fan since now owning the Marantz Ruby CD/Integrated.
P.S. Owned the Rotel 990 power amp years ago. That amp had lots of low end grunt for sure. But it did not have that engaging musical quality of the Marantz gear.