I have the NR1403 that I bought (
refurbished for $270, if you are interested)
All subsequent (and more expensive) models only have upgraded features. The preamp and poweramp quality and Audussey room correction are the same... to my knowledge. In my case, I really didn't want all the bells and whistles - my $100 Roku has more features anyway, and I would rather upgrade a source (like Roku) to get features than get have it become obsolete in a much more expensive AVR that I would be upgrading much less often.
Anyway, only my personal thoughts. Many people like integrated features too.
This is a lovely little AVR. I am surprised at how much Marantz has been able to cram into their slimline AVRs. Setup was an absolute breeze - even Audussey setup took 2 minutes at most. And Marantz has really good audio quality for an AVR. Being so slim, it still outputs 50 watts per channel in stereo mode. That is not a lot but with sensitive speakers, that can work.
In my case, I have a pair of floorstanders with moderate power requirements. I did have to crank up the volume to at least 1 oh clock - 2 oh clock to get decent volumes. And since I have a fairly tight and airless cabinet, the AVR would start heating up a bit (it has a temperature display or what seems be a temperature display). But when I say heating up, only the display shows higher temp - I never had an occasion when the amp shut down or went into protection mode.
However, my intent all along was to use this AVR as a stereo preamp (that accepts HDMI and has an inbuilt DAC). Considering this AVR is so small it is as big as a general preamp (or thickish CD player), and is also one of the rare entry level AVRs that has pre outs, it ticked all my boxes. And the price is really sweet too.
I have now been using it as a preamp and the sound quality jumped quite a bit. It was still decent to begin with, but my speakers have really benefited from the extra muscle that my power amp provides.
In short, two thumbs up for this tiny little AVR with such a big heart. And it does really well where it matters - sound quality. It also has a mode that significantly improves crappy input audio quality - like 128kbps mp3s or streaming internet radio.