As @elliottdesigns said, and going by the attached photo I will put the HDMI in to the too hard basket for now.
Better option would be the optical, I am concerned however about converting the signal from digital -> analog -> digital -> analog. Not sure if that will have an effect of the end signal quality.
I still have the option of using the bluetooth, however the concern there is the connection reliability (although I’ve heard that BT 5.0 is quite reliable), and the need to use time delay when watching TV to sync the picture and sound.
Arylic should work as they have the S/PDIF IN expansion board that does exactly what I need. The problem is they only offer 50W per channel @ 4Ohm, and the DSP looks not-so-advanced compared to the KABD’s sigma studio, I might be wrong though, not sure.
Thanks @ajc9988 for the good advice about finishing the build in my head first before I make a hole in my pocket. I will have fun though no matter what I decide. I am starting to think that maybe buying both the Arlyc and the KABD and see how they sound, play with the DSP’s and assess the amps etc, before I make the decision on what to use and finish the build.