Gthrush1 is right that there is a lot of music worth a listen, but this is one area where I think a little effort is well spent. While I often do not hear the significant differences between specific cables or tweaks that others do, the difference in my system between toslink and coax was not subtle and much in favor of coax.
Toslink vs. RCA
In virtually every review of DACs and jitter reduction devices, RCA seems to be better than TOSLINK for the transmission of S/PDIF. This seems strange to me considering that a whole host of nasties like EMI and transmission line effects can be eliminated with optical transmission. Does anyone know why RCA is better?