Bwyoung, hi. I'm not aware of any premium FireWire cables but they are sure to be around somewhere. S/PDIF cables abound of course, and I've tried several, from Canare Digiflex (your current cable and a terrific value) up in order of price through Apogee Wyde Eye to VH Audio cryo Pulsar, Zu Ash, Wireworld Gold Starlight and the Atlas Opus I own now.
I've found that the S/PDIF cable's quality makes a big difference but even more important is cable length. In my setup a 1.5m length of Apogee Wyde Rye beat a 1m length of it for coherence and clarity. Others have found the same, including UHF Magazine and its Audiophile Store.
The M-Audio FireWire-to-S/PDIF converter is another key element. I don't know yours but I use a M-Audio Audiophile USB from time to time, to change USB to S/PDIF. It is dated now and a 60-dollar Valab converter box from eBay does the job better, especially in the highs.
Just as a rule of thumb, I would have thought a fair budget for the outboard gear, when you compared, would be the price of the CD player minus the price of its DAC (which you are of course using in the comparison). Hard to put a dollar value on just part of the unit, of course.
