There may be differing opinions on cables, but in my opinion when it comes to digital optical cables , brand name etc. makes no difference. It is passing digital information, quality of sound will not be affected by different cables. However since you will be using an optical cable vs. HDMI you will not be able to use the lossless PCM audio on blueray, you will be stuck using dolby digital, optical cable does not have the bandwith to support the newer audio formats on blueray.
I recently upgraded my monitor to a 1080p plasma. I thought the same theory was true to hdmi cables as it is with optical cables(digital info is unaffected by brand, price of cable), the salesguy at BB talked me into purchasing new hdmi cables, he stated older hdmi cables may not have enough bandwith to support 1080p. I did go ahead and get new cables, but I am still not sure about the truth of this. Hopefully someone with more knowledge than I will chime in and can clarify this.