Of streamers, digital output and clock

[thumb5]

What cost effective options could I consider to continue to be able to stream Amazon music and free that RCA input?

An S-P/DIF to Toslink converter into one of the optical inputs on the 120 would be very cost-effective and would free up the coax/RCA input.

Would a SPDIF to USB interface such as a Mutec MC 1.1 or 1.2 allow me to enter the Devialet through a USB-B to USB-B cable? Or is that output usable only with a computer?

I don't think this will work. The general rule with (old-style) USB is that you if you are considering using a non-standard cable, then there is a good chance that what you're connecting is not designed to work together. In particular, having a type-B socket means that the device is a USB peripheral and will only work when connected to a host (type-A). Connecting the Mutec MC 1.2 to the USB socket on your Devialet would mean two peripherals connected together, which won't do anything useful.