From what I've read, copper will will give you a deeper, fuller bass. Silver a more airy/detailed top end. (some silver cables may be to bright) For speaker cables I'm currently using a pair of Jena Labs Valkyre (copper) on the bottom (my speakers are bi-wireable) and Xindak fs-2 on the top. The fs-2's are a silver and copper sandwiched design so I'm getting the detailed and airy top from my tweeter's and the copper brings in the lower end of the mid-range drivers. With this s/c combo I've used both copper and silver i/c's with good results. Currently I'm using Shunyata Aries S i/c's (copper) and the sound is outstanding.
The Valkyre's are wonderful cables and when my budget permits I'll get another pair to try on the top but for now I'm very happy with this silver/copper combo.
The Valkyre's are wonderful cables and when my budget permits I'll get another pair to try on the top but for now I'm very happy with this silver/copper combo.