It makes sense comparing Denon AVR-S640H vs Onkyo TX-8020 because they both are able to give some premium features.
A significant difference between the receivers in the number of channels, Denon AVR-S640H has 5.2 versus 2.0 for Onkyo TX-8020. Regarding power, then AVR-S640H has such a W/Ohm ratio - 75/8, 100/6 when TX-8020 has a power of 90/6. The THD is 0.08% for the AVR-S640H but 0.03% for the TX-8020.
Characteristics of digital to analog converter (DAC) are different, 192 KHz/32-bit for AVR-S640H and 192 KHz/24-bit for the TX-8020. None of the models support Bi-amping. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing.
Only the Denon AVR-S640H can connect to the Internet via WI-FI. Only the AVR-S640H has Bluetooth support. The Denon AVR-S640H has support for AirPlay, AirPlay 2, and its competitor in our comparison - AirPlay. Only the AVR-S640H supports Spotify.
Only the Denon AVR-S640H has support for High dynamic range (HDR). Only the AVR-S640H provides HDMI signal transmission in standby mode. Both competitors are not able to scale the HDMI signal. Dolby Vision technology found support only on the AVR-S640H. Only the AVR-S640H supports HDMI Audio Return Channel (ARC). Unfortunately, HDMI eARC is not available on monitored devices. Of the two receivers in our comparison, HDMI CEC is present in only the AVR-S640H. These compared receivers have a built-in phono stage for connecting a vinyl player. An ECO mode is only available for the AVR-S640H. The setup assistant will help you configure Denon AVR-S640H.
None of the rivals equipped with Dolby Atmos multichannel audio decoder. The receivers do not support the surround sound technology DTS:X.
The Denon AVR-S640H is better receiver in this comparison. Check Denon AVR-S640H price