The main differences will be how the auto setup and room correction software deal with things. Ypao, mcacc audyssey, Dirac and anthem etc all do it a little differently. No way to know what one will do differently vs another. Another key is navigating menus. For ME, while I do like the performance of many Yamaha AVR’s, I will never buy another one. Simply because I really dislike the menu structure, and they’re proprietary language and one off ways of doing things. Mostly the other brands are navigable and intuitive enough. I do enjoy my Marantz a lot despite some small quirks and will
Use it for a long time.
For you, it seems to me that the price hike from the denon to the Marantz isn’t high enough to be a deal breaker, while the difference from the Marantz to the anthem, almost 1k, while being roughly 1500 over the denon.(can buy a very nice AVR for that price gap lol) I estimate that to be well into diminishing returns, which of course for most people that would qualify. But if you have an ample budget, only you can decide where that line is. From here, it looks like the Marantz is right about where your comfort level is if not slightly above. FWIW, I think you’d love it.
And also, happy new year to you!