Switch to silver for a treble boost?

Carl, based on what I know of you in our discussions, I would suggest that upgrading over time in components will yield more of the air/sparkle, etc. you seek. You would be better off pursuing saving for upgrade to your components or speakers at this point. The distinction between silver/copper cables can be less exceptional (in many cases) than component changes. I would encourage you not to lose sight of a higher goal by taking a quick upgrade.
This is especially so if you have some upper frequency hearing loss.

If I had to send you in one direction to start, it would be upgrading speakers. A world of good things can happen at both ends of frequ. spectrum with a speaker upgrade. It may take much longer to save up for, but it is well worth it. You can ask similar questions in regard to the presentation of speakers when the time comes to narrow down the field.

You might find temporary satisfaction in a cable change now, but the rig is primed for other upgrades prior to cables. It depends on how far you want to take it. If you never want to keep extending the main rig, then get the cables.

Knownothing, from my experience reviewing speakers ribbon tweeters are among the most detailed and open I have heard. I very much enjoy the neo-ribbon used in the Legacy Audio Focus HD. Moving down on my list I would then suggest a dual ring tweeter like the one in the Von Schweikert speakers, and finally a metal dome tweeter.

Moving from an entry level monitor to a mid level floor stander is revelatory. Paradigm speakers have always sounded to me clear and detailed at the top end, and I also have enjoyed planars, which with companies like Magneplanar and Eminent Technology offer a lot of openness in the high end at affordable prices.