Digital Cables in Cambridge Audio D500

I have a Cambridge Audio D500 CD player, and I'm considering getting a Cambridge Audio S700 DAC to add to it. I'm looking to get a more airy sound, a little more detail, and better distinction between instruments. What type of digital cable should I get (it has TOSLINK and BNC connectors)? At this level of equipment, do higher quality digital cables make much of a difference? I currently plan to use the lowest level of Transparent Audio's Digital cable. I'm using Transparent Audio MusicLink SuperXL RCA's for the analog connection right now. Any cheap digital cable recomendations (under $250)?

Thanks,
Gil