Coax is a good option - better than optical. Optical is much more succeptible to causing jitter in the data stream.
I'll 2nd the Apogee. They're a great company and really understand digital. I wouldn't hesitate to use their cables in any situation.
The issue of good, better and best cable for a digital connection is really pushing it, though. Get a cable that passes all the bits without picking up noise and adding jitter and you're fine. There's no need to spend too much money on one of these cables. I use Monster Data-1000 and Apogee and haven't noticed any degradation in signal. I'm using them in a studio with high-end recording equipment and all the gear involved is happy. I've compared the signal I sent through these cables with the signal that arrived and it's IDENTICAL. That's all there is to it. Of course certain lower end equipment might be more likely to cause errors with these cables, but you're safe with the Apogee or the Datalink-1000.
I realize that this is a pretty esoteric forum dedicated to tweaking, and I'm one of those people who's likely to spend hour after hour nitpicking my cable runs, but even I know when to say "that's good enough." Rest assured that you're $100 will get you a top-notch cable. In fact, you don't even need to spend that much - an Apogee 3 meter Wyde-Eye s/pdif cable is only $59.90 direct from them at apogeedigital.com. And no I don't work for the company, I've just been using their stuff for many years.
