Fosi Audio ZD3 Desktop DAC Preamplifier, Full Balanced Digital to Analog Audio Converter with ES9039Q2M, Bluetooth/USB/Optical/COAX/TV HDMI ARC Input, XLR/RCA Output with Remote Control

You Fine Arts R1 will drive the MB Quarts capably, if not to their limits. I would recommend this DAC: Fosi ZD3, currently on sale during Amazon's Summer Prime Days for €161.49. It checks all your boxes with both optical and HDMI ARC, giving you two options to connect your TV (including audio from your PlayStation), USB for your phone (or computer), and Lossless Bluetooth. It also has a remote control to make switching between your various sources easy. You would connect it to the DSR/AUX input on your Grundig. Enjoy! P.S. I was in Cologne back in April, toured the city, and grabbed a quick bite at Funkhaus!