Having had an opportunity to test Onkyo TX-RZ840 vs Denon AVR-X2500H, I’d like to share my impression here to facilitate your choice of a new AV receiver.
The number of channels for receivers is different - 9.2 versus 7.2, respectively, for devices. In terms of power, there are differences, the TX-RZ840 has such a ratio W/Ohm - 180/6, while the AVR-X2500H has a power of 95/8, 125/6. A common feature for devices is the same total harmonic distortion - 0.08%.
The manufacturer installed different DACs, the TX-RZ840 received the model AKM 384 KHz/32-bit, but the AVR-X2500H is equipped with AK4490 384 KHz/32-bit. Each of the compared opponents supports Bi-amping. Both Onkyo TX-RZ840 and Denon AVR-X2500H can transmit an audio signal directly to the amplifier and bypasses any DSP processing.
Wireless Internet access via WIFI is possible on both units. Each of the receivers has a Bluetooth connector. Both devices can work with such Apple Music services: AirPlay, AirPlay 2. Access to the Spotify service is on each of the competitors. The number of available streaming services varies for receivers, the Onkyo TX-RZ840 works with Deezer, TIDAL, Pandora, TuneIn Radio, but the Denon AVR-X2500H works with Deezer, TIDAL, Pandora, Napster, SiriusXM, TuneIn Radio, iHeart Radio, Sound Cloud.
The HDR10 function is present in each of the rivals. The quality of 4K/60Hz signal remains unchanged when transmitting from a source to a TV or projector via HDMI for both receivers. Signaling over HDMI in standby mode can provide the TX-RZ840 and the AVR-X2500H. None of the devices can increase the resolution of the incoming video signal. Each of the participants of the comparison has a Dolby Vision.
The number of HDMI inputs/outputs varies depending on the receiver, the TX-RZ840 has 7/2, and the AVR-X2500H has 8/2. HDMI Audio Return Channel is implemented in both devices. HDMI eARC is only supported by the TX-RZ840. When comparing receivers, it becomes clear that each of the rivals can work with HDMI CEC. TX-RZ840 and AVR-X2500H support the standard HDCP 2.2. Like most receivers, our models have a built-in phono stage for connecting a vinyl player.
Unlike the TX-RZ840 where 3 Multi zones is provided, the AVR-X2500H works with 2 Multi zones. For voice control in the TX-RZ840 is used Google Assistant, but in the AVR-X2500H is used Amazon Alexa, Google Assistant, Siri, Josh.AI. There is an ECO mode in AVR-X2500H. The Onkyo TX-RZ840 and the Denon AVR-X2500H can be properly configured using the setup assistant.
A Dolby Atmos multichannel audio format is available both models. A DTS:X surround technology is supported by devices from our comparison.