There are a couple of great Beryllium tweeters. D3004/6640, TW29-B, D2908-7140, etc ... You have Raal. And more. Yet for me, I will mirror what others have posted. A good AMT just sounds very real to this 40 yr musician veteran's ears. I love some Aruum Cantus. And although I'm not a fan of Heil dipole tweeters, I love the old round face monopole AMTs! If crossed over high enough in a 3 or 4 way, they are among the best available today.
What speaker has the best tweeter?
I love the AMT tweeters in my speakers. They are definitely different from other tweeters I have heard. I enjoy their openness and air. But there are qualities of other tweeters that excel in other ways. Some v pricy speakers use beryllium or diamond or diamond coated beryllium. I see that the price of, Seas I think, diamond tweeter is like $6K a pair. Then ribbons offer used. Not to mention plasma, etc.