bc,
That should work just fine since the Audigy is internal and the Stereolink is connected via USB. If you are using Windows you will need to change the active output device in addition to selecting a different input on the stereo. With the Stereolink they suggest running the volume on the PC all the way up and controling the level with the stereo.
Keep in mind that some preamps/receivers manipulate some of the inputs. Most don't but be aware of the possibility. Also, try and match the levels. If they are not closely matched the louder one will tend to sound better.
HTH,
Mike