It makes sense comparing Denon AVR-X8500HSP vs Onkyo TX-NR595 because they both are able to give some premium features.
A significant difference between the receivers in the number of channels, Denon AVR-X8500HSP has 13.2 versus 7.2 for Onkyo TX-NR595. Regarding power, then AVR-X8500HSP has such a W/Ohm ratio - 150/8, 190/6 when TX-NR595 has a power of 80/8, 170/6. The THD is 0.05% for the AVR-X8500HSP but 0.08% for the TX-NR595.
Characteristics of digital to analog converter (DAC) are different, AK4490 384 KHz/32-bit for AVR-X8500HSP and AKM 384 KHz/32-bit for the TX-NR595. Both the AVR-X8500HSP and the TX-NR595 support Bi-amping. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Rivals from our review have Bluetooth support. The Apple Music service is implemented on considered devices: AirPlay, AirPlay 2. Spotify can be used on each receiver. The AVR-X8500HSP can work with the audio stream from Deezer, TIDAL, Pandora, Napster, SiriusXM, TuneIn Radio, iHeart Radio, Sound Cloud, and the TX-NR595 can receive a content from Deezer, TIDAL, Pandora, TuneIn Radio. Compared AV receivers retain the quality of 4K/60Hz signal when transmitting from a source to a TV or projector. HDMI signal transmission in standby mode is implemented in each of the devices. Both rivals can scale the resolution of the incoming HDMI signal. The HDR standard - Dolby Vision is supported by these receivers.
The Denon AVR-X8500HSP has 8/3 HDMI inputs/outputs versus 6/2 HDMI connectors of the Onkyo TX-NR595. The HDMI Audio Return Channel (ARC) feature supports both devices. The HDMI eARC is available only on the AVR-X8500HSP. The Consumer Electronics Control (CEC) feature is present in most modern AV receivers and the models in our comparison are no exception. Both models support the standard HDCP 2.2. These compared receivers have a built-in phono stage for connecting a vinyl player.
The AVR-X8500HSP supports 3 Multi-room zones, versus 2 for the TX-NR595. The AVR-X8500HSP supports voice control via Amazon Alexa, Google Assistant, Siri, Josh.AI, and the TX-NR595 - Google Assistant. An ECO mode is only available for the AVR-X8500HSP. Both AVR-X8500HSP and TX-NR595 can be configured using the Setup assistant.
Both devices have support for Dolby Atmos multichannel audio format. The surround sound technology DTS:X is supported by devices under review.