Does your Marantz have DAC built in? If so, does it have a USB input? If so, I’d start simple and get an RPi 4B, RPi power supply, and a basic RPi case, a 16GB SD card and load MoOde onto the SD card. You can access the MoOde UI via a web browser. Try streaming with this setup before investing in a HAT for the RPi. if your Marantz doesn’t have have a USB DAC, but optical and/or coax I’d get a Hifiberry Digi+ Pro HAT for the RPi and a Hifiberry case. If your Marantz doesn’t have a DAC, I’d look into getting a unit like the Allo Boss2 Player. You could go with one of the Hifiberry DACs, but I’m not sure of the compatibility of new Hifiberry DAC with MoOde. Also, asked on reviews Allo is the better DAC. Honestly, this maybe the best option regardless of your Marantz’s DAC status.