hairystuff :
The optical input connector on the audigy can only accept 2 channel stereo PCM, you have to adjust the audio output setting on the ps3 to get an output which is compatible with the audigy.
I'm having the same concern. I was intending to transfer a digital 5.1 sound source from an HD streamer to the sound card via the optical in via toslink cable.
So you're saying the sound card's digital input (optical toslink input) can only get digital stereo? How would the digital sound be outputted? Through the sound card's analogue outputs or via the sound card's digital output, which goes to a device that decodes the digital stereo to digital surround?
How much better would the sound be if the OP did what you said as opposed to using a regular stereo cable, from PS3 analogue output to the sound card's analogue input?
"Analogue" as in either 1/8mm (3.5mm) mini-jacks or RCA jacks.