An affordable AV receiver is always a good option to consider, so Denon AVR-S660H vs Denon AVR-S740H comparison definitely makes sense.
A significant difference between the receivers in the number of channels, Denon AVR-S660H has 5.2 versus 7.2 for Denon AVR-S740H. Regarding power, then AVR-S660H has such a W/Ohm ratio - 75/8, 100/6 when AVR-S740H has a power of 75/8, 110/6. The THD is the same and is 0.08%.
Competitors' digital to analog converter (DAC) is identical to 192 KHz/32-bit. None of the models support Bi-amping. The Denon AVR-S740H can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Rivals from our review have Bluetooth support. The Apple Music service is implemented on considered devices: AirPlay, AirPlay 2. Spotify can be used on each receiver. The AVR-S660H can work with the audio stream from Deezer, TIDAL, Pandora, SiriusXM, Napster, SoundCloud, and the AVR-S740H can receive a content from Deezer, TIDAL, Pandora, Napster, SiriusXM, TuneIn Radio, iHeart Radio, Sound Cloud. HDMI signal transmission in standby mode is implemented in each of the devices. The AVR-S660H can scale the input HDMI signal, unlike the AVR-S740H. The HDR standard - Dolby Vision is supported by these receivers.
Each receiver has 6/1 HDMI inputs/outputs. The HDMI Audio Return Channel (ARC) feature supports both devices. The HDMI eARC is available only on the AVR-S660H. The Consumer Electronics Control (CEC) feature is present in most modern AV receivers and the models in our comparison are no exception. The AVR-S660H supports the protection of digital content of the standard HDCP 2.3, versus HDCP 2.2 in the AVR-S740H. These compared receivers have a built-in phono stage for connecting a vinyl player. Supported voice control technologies are identical - Amazon Alexa, Google Assistant, Siri, Josh.AI. It is also worth noting that the ECO mode is presented in each of the receivers. Both AVR-S660H and AVR-S740H can be configured using the Setup assistant.
Only the AVR-S740H has a Dolby Atmos multichannel audio format support. A surround technology DTS:X is supported only by the AVR-S740H.