An affordable AV receiver is always a good option to consider, so Onkyo TX-RZ820 vs Sony STR DH550 comparison definitely makes sense.
A significant difference between the receivers in the number of channels, Onkyo TX-RZ820 has 7.2 versus 5.2 for Sony STR DH550. Regarding power, then TX-RZ820 has such a W/Ohm ratio - 160/8 when STR DH550 has a power of 90/6. The THD is 0.08% for the TX-RZ820 but 0.09% for the STR DH550.
Characteristics of digital to analog converter (DAC) are different, AK4458 384 KHz/32-bit for TX-RZ820 and 192 KHz/24-bit for the STR DH550. Only the TX-RZ820 supports Bi-amping feature. The Onkyo TX-RZ820 can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Only the TX-RZ820 has Bluetooth support. Only the TX-RZ820 supports Spotify. Only the TX-RZ820 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-RZ820.
The Onkyo TX-RZ820 has 7/2 HDMI inputs/outputs versus 4/1 HDMI connectors of the Sony STR DH550. The HDMI Audio Return Channel (ARC) feature supports both devices. Unfortunately, HDMI eARC is not available on monitored devices. 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. The TX-RZ820 has a built-in phono stage for connecting a vinyl player. A voice control is not available. An ECO mode is only available for the TX-RZ820. The setup assistant will help you configure Onkyo TX-RZ820.
Only the TX-RZ820 has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the TX-RZ820.