It was just a suggestion for folks who want to experiment.I wouldn't bother with BNC-RCA digital coax in Digione setup. A good quality BNC-RCA digital coax will cost more than RPI+Digione put together and no matter what, I am not a proponent of spending more on cables than the equipment itself. A good 75Ohm RCA coax cable with right terminations around 1-2K should work well.
In my rig, I just use whatever is available at home (in my cable box/carton)
Old MX RCAs, some old component video cables, and now a set of cables from Allo (cheap stuff, but firm contact)
Speaker wires are Finolex 2.5 sqmm
Banana plugs from MediaBridge
Cheers,
Raghu