Audio driver: WMA-Pro over S/PDIF

Hi,
does anyone know if there is an SoundMAX driver which supports 'WMA-Pro over
S/PDIF'? In my Media Player the option is greyed out :-(.
If not - are there external audio adapter existing which supports this
function? I found less information in google about this topic. I tried it
with the Audigy NX but this external adapter does not support the output of
WMA via digital out - I only get Stereo sound...

Regards,
Thomas