It makes sense comparing Onkyo TX-NR575 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, Onkyo TX-NR575 has 7.2 versus 2.0 for Onkyo TX-8020. Regarding power, then TX-NR575 has such a W/Ohm ratio - 135/6 when TX-8020 has a power of 90/6. The THD is 0.08% for the TX-NR575 but 0.03% for the TX-8020.
Characteristics of digital to analog converter (DAC) are different, 384 KHz/32-bit for TX-NR575 and 192 KHz/24-bit for the TX-8020. Only the TX-NR575 supports Bi-amping feature. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Only the TX-NR575 has Bluetooth support. The Onkyo TX-NR575 has support for AirPlay, AirPlay 2, and its competitor in our comparison - AirPlay. Only the TX-NR575 supports Spotify. Only the TX-NR575 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 TX-NR575. Only the TX-NR575 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 TX-NR575. These compared receivers have a built-in phono stage for connecting a vinyl player. A voice control is not available. An ECO mode is not present in each of the AV receivers. The setup assistant will help you configure Onkyo TX-NR575.
Only the TX-NR575 has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the TX-NR575.