You might want to add to your list
ESS, at one point (later, I think) the maker/marketer of the Heil AMT (Air Motion Transformer), and used it in comb with 8' 10" or 12" woofs in cabinet.
I forget the name just now.
The AMT is a bit tricky and I am not sure that I completely understand it. It's an ESL and inside it is flat, so I guess it's a planar.
I've got a pair but have not yet had time to open.