Good day,
You can connect your TV directly to the Soundbar and have a better sound than with the built-in speakers of your TV. If you connect a Blueray / DVD player or game console directly to the TV, the sound from these sources will also come out of the Soundbar.

You would only need the AV receiver (Marantz) if you have speakers without a built-in amplifier.

I don't see how AV receiver and soundbar together would make sense.

Kind regards