In response to your question "are there sonic differences between" copper and silver ICs, I would answer yes there are, with the provisos that the quality of either's conductors must also be considered, as should the location in the system, and the components, and ...
After 5 months looking for ICs that fill my requirements, in my system, I can appreciate your desire to limit your choices. Unfortunately, to provide some help, I think most responders would like to know what application (CD to Pre, Pre to Amp, etc.) the ICs will be used in, and what sonic characteristics YOU are seeking in the end. Simply stating that silver ICs provide greater resolution, but may have a tendency to be too bright might cause you to believe that silver will make your ears bleed. Some smart people here (not a self inclusive statement – 5 months and counting) might be able to help you reach your endpoint with a minimum amount of frustration during the journey if they are given just a bit more information.
