What's this tweeter upgrade some people have been talking about?
For $170 plus shipping, you can buy from Divergent Technologies the tweeters and capacitors that are now being used in the De Capo i speakers. They will fit the old non-i De Capos, assuming you have a later model with tweeters attached with four screws. If yours only have three screws, you'll not be able to do the "upgrade."
The reason I put upgrade in quotes is because I did not notice a dramatic difference in the sound of the speakers with the new tweeeters. Although some have made mention that the new tweeters tamed an alleged brightness or peak in the midrange of the old tweeter, I never found that to be a problem with mine. To be honest, I really think that my $170 would have been better spent elsewhere (like on more music).
I think you'll find others around here who noticed more of an improvement after the changeover to the new tweeters, so stay tuned for more input.