Having had an opportunity to test Onkyo TX-SR353 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 - 5.1 versus 7.2, respectively, for devices. In terms of power, there are differences, the TX-SR353 has such a ratio W/Ohm - 140/6, 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-SR353 received the model 192 KHz/24-bit, but the AVR-X2500H is equipped with AK4490 384 KHz/32-bit. The Bi-amping function is implemented only in the Denon AVR-X2500H. The model AVR-X2500H can transmit an audio signal directly to the amplifier and bypasses any DSP processing.
Wireless Internet connection via WIFI is only possible with AVR-X2500H. Each of the receivers has a Bluetooth connector. The AVR-X2500H has access to the Spotify service. Signaling over HDMI in standby mode can provide the TX-SR353 and the AVR-X2500H. None of the devices can increase the resolution of the incoming video signal. Operation with the Dolby Vision is only possible with the AVR-X2500H.
The number of HDMI inputs/outputs varies depending on the receiver, the TX-SR353 has 4/1, and the AVR-X2500H has 8/2. HDMI Audio Return Channel is implemented in both devices. HDMI eARC is not supported by the TX-SR353 and the AVR-X2500H. When comparing receivers, it becomes clear that each of the rivals can work with HDMI CEC. TX-SR353 and AVR-X2500H support the standard HDCP 2.2. In the presence of a built-in phono stage for connecting a vinyl player only at Denon AVR-X2500H. There is an ECO mode in AVR-X2500H. The Denon AVR-X2500H can be properly configured using the setup assistant.
A Dolby Atmos multichannel audio format is available only in the AVR-X2500H. Only in the AVR-X2500H realized a DTS:X surround technology.