I was definitely a 2Ch analog snob back then. I was so hardcore about not even using a pre-pro for 7.1 surround sound!
Now some people asked, "How can you do 7.1 surround sound using just 2ch analog stereo preamps?"
Well, at one point, I had 4 Acurus RL11 class-A analog preamps.
This Acurus preamp didn't even have TONE controls! It was so "pure" it only had balance and volume control.
I would use the 7.1 analog outputs from my Denon BD player and hooked to those 4 analog stereo amps. Crazy.
But then I did a comparison between a $500 AVR in Direct Mode vs my pure class-A Acurus preamp. The sound from the AVR in Direct Mode was just as crystal clear as the stereo preamp. I couldn't believe it. The measurements show it. But it's still difficult for any analog guy to accept that even a pre-pro could match the clarity of an analog preamp, much less an AVR for crying out loud!
So IMO, if you only use Direct mode and don't care for things like Subwoofer EQ and Dynamic EQ, then stereo preamp, pre-pro, or AVR would all work just as well.
What is interesting is that you think the Marantz integrated amp sounded like crap! I wonder if there is a Direct mode on that Marantz?
Not all components have direct mode. For example, I used to own a $1,500 Pioneer Processor that did NOT even have a direct mode. I mean the closest thing was a Stereo mode. But when compared to the Acurus preamp and $500 AVR, the Pioneer processor sounded like crap too because there was some obvious tone control in the background. There was no "Direct Mode" button.