I've kicked the SR5006 around for a week now and here are my impressions so far, and some comparisons with the Class D Panasonic SA-XR57, which it replaced:
The SR5006 is obviously larger and it runs hotter than the Panasonic SA-XR57. The sound is comparable, although at first listen, in Stereo it seems a little less powerful than the Panasonic (which can use two amps per speaker in Stereo mode) -- not sure if this is necessarily true, will have to try it again (Gallo Solo speakers).
The Audyssey room correction and other enhancements provide a clearly noticeable difference to 7.1 movie listening, mainly in helping to enhance the dialog. This is the (only) one improvement which is making me keep this otherwise large/hot box

The Speakers A/B feature is largely useless, since the room correction and other Audyssay settings for Speakers A are passed to Speakers B, and turning it off is a chore. The Marantz also keep running the surround speakers at the same time with Speakers B, which is idiotic. I had to resort to using Zone 2, which of course does NOT accept any digital input. I am feeding the analog out to a Stereo
Class D amp (Tripath TAA4100 - I love that little amp, not made anymore, AFAIK). Since I have to get the signal out of my HTPC, I just placed a pre-order for the super-cheap
FiiO E10 DAC, which should provide enough of an improvement for what I need.
Overall, playing stereo music in a second room is much, much harder to achieve with the Marantz, than it was with the Panasonic (which required one button push).
The NET Radio features of the Marantz are somewhat disappointing, at least measured against my HTPC experience. Make that outright primitive, in terms of ease of use and GUI. Pandora "stations" cannot be saved as presets, nor can internet stations be saved as presets for Zone 2 (this is from Marantz second tier tech support -- BTW, the first line of tech support is about as bad as it gets).
So, at the end, I am keeping the receiver,
only because of the Audyssey features. Otherwise, it is not in any way improvement over the Panasonic.
In terms of Stereo playback in a different room, the Marantz is simply not well thought out, although the same can be said about almost every other mainstream receiver on the market.