For those looking to solve a similar situation as I - feeding the Realiser digitally from an audio source (Squeezebox, Airport Express, laptop, CDP, etc.), the Monoprice DVI & S/PDIF Digital Coax/Optical Toslink Audio to HDMI Converter does not work. Guessing it needs a video signal too, but back to square one.
Considering audiophiles are listed as half the Realisers user base, I wish it was a bit less video-centric. ;)