Beryllium Tweeters

I've only heard Paradigms Beryllium Tweeters but I absolutely loved them! What other "affordable" (>$2k new or used) speakers use them and what are your experiences with Beryllium tweeters? What other Tweeters rival the extension, air and sweetness that I was hearing with my Paradigm Sig 2's? DeCappo? Usher? ...?