I've been down this road, and considered an APT series driver as well as the Morel MTS-37. The Morel is a horn loaded soft dome tweeter and is supposed to be an excellent device. I haven't changed parts, but found improvement with the piezo after damping the whole rear of the tweeter with mortite. It seemed to smooth them out a bit and could be attributed to lowering the resonant frequency of the plastic horn, or the increase in mass could have just made it less excitable by the woofer interaction. Or, I'm just crazy. There are certain people around who claim to have tamed the piezo tweeters in other designs with a coat of Dammar varnish. I can't comment on the effectiveness of this, and don't intend to find out. I'd still be interested in trying the APT or Morel out. As you've heard, the Alpha 10 woofer does pretty amazing things in that cabinet. Some of the magic of this design is in it's simplicity though. When going to a different tweeter, this will be lost as either way will require a 2nd or 3rd order network, and varying degrees of attenuation. Still, at the 2 Pi's price point, Wayne has a very unique product. I know of nothing else that will "get it done" like the 2 Pi for the money. Good luck and good listening! Jerrod