Silver plated Copper is the best choice. Silver plating oxidizing is of no consequence as Silver Oxide is almost as conductive as Silver is itself. There is NO reason to ever use Brass. Or gold plating. Yes its shiny and pretty but silver is a much better conductor and Silver Oxide is better than untarnished gold. Choose solid Copper connectors with silver plating. Or solid Silver connectors with Solid silver wire. Always use Solid core unless movement is unavoidable. If you want to know why buy a solid core copper speaker cable and then buy a stranded cable of like size and length. Bet you $20 even your wife will be able to tell the difference listening to them. This is seldom talked about but try it before giving an opinion. I think you will agree.
Jeff