Well, here I am to give my 2 cents, but it isn't needed as it would seem. LOL
I have great respect for Marantz, so not slamming them or their product lines, but you will love the Anthem.
ARC is great, and the software is super helpful even in just tweaking speaker placement. You can run a "quick measure" where you select one speaker, and it just keeps doing the audio "pings" and showing you real-time measurements. If you have the mic at your primary seat, for example, you can adjust and tweak that particular speaker's location to get the best response as possible, then move on to the next speaker and do the same. This allows you to get the absolute best speaker placement from a room response perspective before running any correction. Pretty cool by itself before correcting anything.
Heck, before running ARC I was blown away by the sound that came out of the MRX 1120. Like you said, the 1120 is pretty much the 720 with more amplified channels, but the 1120 has a better Toroidal power supply. How much better? Don't know. That is probably debatable. Anthem claims that the sound is "cleaner," but unless doing a side by side comparison, I doubt that anyone would ever know. Even WITH a side by side comparison, it would probably be tough as the 720 is reported as sounding really great too.
You are going to love it.
