This is not in line with what you wanted to know, and I'm not sure what your total budget is for the solution, but I'd also suggest a Mini-PC based solution used with a USB to Coax converter, if you plan to spend about 25-30K in total.
An Intel NUC would have been perfect, if not for the fact that it does not have a coaxial output. The Celeron version will run to under 15K with RAM and a low-capacity SSD. To use it, you will need a USB to coaxial converter (Hiface/iLink/vLink/etc.). It has enough USB Ports, a mini-HDMI port and a network port. It's just 4" x 4" in size, AND it has an IR receiver (you can use most universal remotes) to boot. But the NUC + converter will run to at least 25-30K.
Asus's (prettier) version of the NUC, the VivoPC, has a built in Optical SPDIF output. But the Celeron VivoPC is just under 20K in itself (with 2GB RAM and a 500GB HDD). The digital interface is optical, not coaxial, and that may not work for you.
Way back, I used to use a WDTV (optical out) with a DAC (Caiman) to play FLACs, but it sounded far, far inferior to my Music PC (which used the analog output of a Xonar STX back then). The WDTV is indeed not exactly a stellar music playing device, but the same PC also beat a Squeezebox touch (built-in DAC) that a friend brought along later.