There is a lot of misinformation in this post which is sad as you typically give good advice. Granted these current crop of Denon receivers aren't built quite to the same standard as the older 58xx series but that was a different era where the super-receiver thrived and audiophiles had bigger budgets and placed more emphasis on sound quality over features. Now a days people want their AV receivers to do everything but make them coffee, though I'm sure if that were an options, they'd want that too.
Denon/Marantz switched to monolithic power amps in their receivers years ago, separating each amp on it's own circuit board to to help increase channel density while also improving CH-CH isolation. The picture you are looking at doesn't do justice to how big that power transformer is and also how much ample heat sinking they are still providing in this model. The 8500H also has a very intelligent power management system if (Eco-Auto) is engaged. It will switch the amp to the lower rails at lower power consumption to reduce heat dissipation and increase efficiency. Once the voltage hits a certain threshold, it automatically biases to the higher rails. It's sorta like a Class G topology, though a bit smarter in some regards.
Even back in the days of the venerable AVR-5805, arguably the best AV receiver ever made, the amps weren't rated at 4 ohms. It's not easy to get UL certification on a receiver that has 10+ channels built in rated at 170wpc/ea. In fact, it's pretty impossible even for a receiver that weighed 100+lbs like the 5805. That said, I found the amp section in that receiver to be very stable and entirely able to drive 300+ watts into 4 ohm loads.
see:
https://www.audioholics.com/av-receiver-reviews/denon-avr-5805/denon-avr-5805-measurements-cont
The power supply was massive and the unit had a 13A consumption rating (I believe it had a15A fuse) which allowed it to draw virtually the entire wall current. I used it to power 9 speakers in my 6,000 ft^3 theater room and never had issues for the 3+ years it remained in my rack.
Consumers should be cheering that Denon is still producing a flagship "almost" super-receiver like the 8500H in today's marketplace. I want to see more, NOT less of this! There isn't another receiver in production today that gives you 13 channels of processing, all the latest in HD audio (including Auro 3D) and video codecs with HDMI 2.0 switching all with the added bonus of a pretty damn good amp section that will drive a wide variety of today's loudspeakers. I can't imagine anyone purchasing this rting eceiver would be dissatisfied with the performance. If more power is needed, that's why it has preamp outputs.