I have both a Denon x3100 and an Anthem mrx1140. To answer your questions.
1) no it's not silly to make the switch as long as you are happy and it has all the features you want.
2) no I don't think Anthem is overrated. Their current generation has an excellent pre amp section, multiple independent subwoofer support and great headroom in their class a/b amp channels. Also ARC is excellent and their software is very flexible and the web interface is much better than using an onboard UI like my old Denon.
3) the main difference would be ensuring you get Audyssey xt32 so you can adjust the target curve, getting true multiple independent subwoofer outputs, and the extra power gets you more headroom in the amplifier section which improves things like "impact." So pick the one that best meets your needs.
Here is a good article from Audioholics on the current gen mrx measurements.
In this bench test report of the Anthem MRX 740 & 1140 AV receivers, preamp & amplifier performance is evaluated and compared. We cover Bass management and amplifier matrixing performance recommendations.