See Choosing a Receiver for movies thread, below. Mainly, the differences are in features as the Denon has arguably equal power and better processing. The Denon has Auto EQ/Set-up functions which work well. I don't know if the Marantz has assignable surround speakers for zone1 or 2. Not apples to apples, but as a pre-pro, way better functioning and sounding than my SR-7200(which I really liked). If you are in no rush, you could wait and see/listen as Marantz has been known to hit a home run once in a while. I'm sure next years models will add features to compete with Denon/Yam with regards to the convenience/ home theater side. Oh, one thing I will say, the Denon remote is fair and not as good as the one I had with the 7200. I use a Theater Master, 500 anyway. Lastly, Marantz has had some QC issues of late and I had a Marantz- MM9000 5 channel amp, lost a channel, had it in Factory authorized repair for 4 months,only to be told, it can't be/ not worht fixing--just out of warranty. Not very satisfying to chunk a 50# weight in the garbage in a little over 2 years. Ps-when I got it back, no channels worked?
If I'm correct the MA's are a little forward and bright so I would say a Marantz is definitely a better choice than a Denon. Before you buy anything you should listen to both with _your_ speakers to know for sure which sounds better. The SR7500 sure looks interesting.