I am 99% sure your power monitors do not have SPDIF inputs. You'll need some sort of audio interface to use SPDIF. Then you'll need some sort of software to rout the SPDIF input to the analog outputs to drive the monitors. Most audio interfaces include software as part of the package, I think. But why do you want to use SPDIF to drive your monitors? SPDIF is usually use for recording purposes.   The problem is data conversion. SPDIF is digital. Your powered monitors are analog. You'll need an