Thanks for the suggestions. I haven't heard of a couple of those companies, but I’ll definitely check them out. If there are any more let me know.
Have I ruled out ribbons? No. There’s just something about AMTs that I like better, but I don’t know why. I haven’t been able to put my finger on it. They sound just slightly different. And the other reason is from everything I’ve read, ribbons don’t live as long as AMTs. Don’t know if that’s true or not. Maybe somebody can confirm or deny that.
Ribbons are not as robust as AMTs, so I think the problem is more that the ribbons get employed in sub-optimal designs. Ribbons mostly belong in 3-way designs. They don't handle midrange frequencies well and can be overdriven and destroyed if tasked to play in mids. I wouldn't think that, if properly used, they won't last a long time. Just stay away from ribbons in 2-way designs unless you know the crossover frequency and you know that particular ribbon can handle it easily.
As for AMTs, I have heard plenty, and I think, like other driver types, there are good ones and not so good ones. Some of the best I have encountered were in the Aurum Cantus AMTs that RBH uses in their Signature SV line. The AMT in the new ML XTi line is very good as well. Some others have been, eh, not so great. I am not a huge fan of the AMTs in Golden Ear speakers, for example. While there are plenty of cheap speakers that use AMT tweeters, I don't think you can get a good AMTs cheaply. But I wouldn't get hung up on driver types. I would be looking more at the kind of end performance that you prefer rather than the means used to get there.
