I’m not familiar with Marantz eq options. I have a Yamaha RXA2060 I’m my HT room 5.1 and a Yamaha RXV681 in my master bedroom 2.1. I had many Yamahas before that and a Sony HTIB at one point in the late 90s.
On my current Yamahas, there is a Natural eq setting that I use with straight for 2.1 , but I’m no purist, I drop into 9ch stereo dsp 5.1 in my HT room a lot. (Listening to music in a German bathtub from all my Monkey Coffins. LOL.
) I also run the subs hot. I am more plain in my bedroom 2.1 setup using straight and avr set with 80hz crossover on the bookshelves for the sub.