Simon, what are your 4K/UltraHD sources? If you get/have sources with dual HDMI 2.0a outputs, you can route 4K/UltraHD video direct to the TV via the main HDMI output and HD audio to the Susano for processing via the "sub" HDMI output. The
Samsung UBD-K8500 UltraHD Blu-ray player is an example of a source with dual HDMI 2.0a outputs. Using this method you can retain use of the Susano well into the future (hopefully) and still enjoy 4K/UltraHD video.
Even without sources with dual HDMI 2.0a outputs, you are able to route video and audio direct to the TV and then output audio from the TV to the Susano. Most TV's will output up to Dolby Digital 5.1 and DTS 5.1 (tough to reliably distinguish from HD audio) via their optical &/or coaxial digital ports.
You're really only limited in how far you can take this by the number of HDMI inputs on your 4K/UltraHD TV.
BTW, any relation to this guy?