An affordable AV receiver is always a good option to consider, so Yamaha RX-S602 vs Onkyo TX-8140 comparison definitely makes sense.
A significant difference between the receivers in the number of channels, Yamaha RX-S602 has 5.1 versus 2.0 for Onkyo TX-8140. Regarding power, then RX-S602 has such a W/Ohm ratio - 80/8, 125/6 when TX-8140 has a power of 80/8, 110/6. The THD is the same and is 0.08%.
Characteristics of digital to analog converter (DAC) are different, Burr-Brown 384 KHz/32-bit for RX-S602 and AK4458 384 KHz/32-bit for the TX-8140. Only the RX-S602 supports Bi-amping feature. Each of the AV receivers can transmit an audio signal directly to the amplifier and bypasses any DSP processing. Rivals from our review have Bluetooth support. Spotify can be used on each receiver. The RX-S602 can work with the audio stream from Deezer, TIDAL, Pandora, Napster, SiriusXM, Qobuz, and the TX-8140 can receive a content from SiriusXM. Only the RX-S602 provides HDMI signal transmission in standby mode. Both competitors are not able to scale the HDMI signal. The HDR standard - Dolby Vision is not supported by these receivers. Only the RX-S602 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 RX-S602. The TX-8140 has a built-in phono stage for connecting a vinyl player. An ECO mode is only available for the RX-S602. Both RX-S602 and TX-8140 can be configured using the Setup assistant.
None of the rivals equipped with Dolby Atmos multichannel audio decoder. The receivers do not support the surround sound technology DTS:X.