I think this is a good step forward, and is something that absolutely should have been done, but is also not a "the sky is no longer falling" issue. The performance disparity between Denon 3500 and earlier versions vs the 3600, or now the 3700, if using the right equipment, is all but meaningless.
In other words, go buy a Denon X3500 for $500. Use a Monoprice Monolith 3/5/7 channel amp for $12-$1500. 95 dB SINAD for up to 7 channels for under 2k. 200/300+ watts/channel with much higher burst. Not many speakers that need any more power than that. No external DAC needed....it won't sound any different. Or just use a 3 channel for the LCR without losing all the other internal amps that are perfectly adequate for the rest of the channels.
For those who already have amps that require more than 1.5 volts to provide full power, the new model will result in a significantly lower SINAD since the older versions clip past this point.
If I were starting from scratch and wanted an AVR and external amp today, and the channel count offered was enough, I'd get an X3500 and Monolith 3 channel amp for $1600 total combined cost. Or another $100 gets you 5 channels on the Mono, which would be kind of silly not to do imo. No real benefit of spending $600 more for the new model.
I'm currently running without an external amp since, even though I probably watch movies louder than the majority of folks here on ASR, the internal Denon amps still provide more power than I need at my typical listening levels. And I'm pretty confident I wouldn't hear any difference between my current 85 dB SINAD and the 95 dB I would get with an external amp. The hobbyist in me is still interested in possibly doing this some day, I just don't think there would be any real world audible difference.