Some people have used alternate units. McCauley and Selenium have been used that I know of. The McCauleys went in some nice cherry horns, and the Seleniums went in some MDF's.

Personally, I'm very fond of the JBL's. The Eminence speakers sound very nice though too, and don't cost near as much. I'm hoping Eminence will become more zealous about making drivers with shorting rings, as they have expressed a desire to reach that market. But they are slow to change and seem to prefer "picking low hanging fruit" right now.