Wireworld S/PDIF cables fit Hugo without adapters if you modify the RCA contact a little bit. Remove the screw and pull the shell back ca 4 mm. Be careful to also move the silicon ring together with the shell, it is hard to get the silicon ring back into the shell again, I know… The friction between the shell and the cable is so high, at least for my Silver Starlight 6 cable, so you don’t need the screw if you are reasonably careful when unplugging the cable. You could always drill another hole in the shell, of course (the screw is threaded into the inner part of the contact, not the shell). Wireworld cables should also fit the line out sockets when modifying the contacts in the same way.
Hmm, I should really get out of my lurking mode soon…