Brass versus copper binding posts

Greetings all. My current speakers are the Usher Dancer Mini-X DMD. I recently removed the press on tabs that connect the internal speaker wires to the drivers and solder them directly with cardas silver. I perceive an increase in sound quality, and as we know perception is reality. I planned on doing the same thing at The binding posts. I assumed they were gold-plated copper. But when I put a small drill point into the end of the threaded post the color stayed the same where I expected to see an obvious copper color. I think this means my binding posts are brass. If I’m correct that seems like a cost saving decision by Usher. Would those of you who know more about this stuff than I do agree it would be worth the time and money needed to switch to some quality gold or rhodium plated copper binding posts? Thanks in advance