A:Answer The Sonos Connect has two digital outputs and one analog output. The difference depends in the quality of the DAC of the Yamaha RX375 versus to one built into the Sonos player.
The Yamaha is using a 192kHz/24-bit Burr-Brown digital-to-analog converter, not sure what chipset, they tend to have better than average electronics.
I never heard really bad opinions regarding the Sonos DAC and when feeding the Yamaha via the analog inputs other DSP circuitry can have a bigger impact on your listening experience. Connect both digital and analog and compare the sound. Go with the one that feels better for your ears, room and music.