I do not see the Bose 901 as being in any way influential, as the basic design is wrong in almost every aspect, technically and aesthetically. (Whether Amar Bose knew this, and manufactured them anyway, will never be known. But the technical literature Bose published contained gross distortions, if not outright lies.) The speaker that preceded it -- the 2201 -- did have some justification, and ought to be reconsidered, using current DSP technology.
Similarly, the Klipschorn has had zero influence. Yes, there are modern horn-loaded speakers, but they're of much-higher quality. Paul Klipsch apparently thought any horn-loaded driver was inherently superior to any direct radiator, the result being some of the worst speakers I've ever heard.
The obvious omission -- as others have noted -- is the QUAD ESL-57, the first practical full-range ESL. Several companies make "pure" and "hybrid" electrostatics, most-notably MartinLogan. And some people still feel that nothing beats the ESL-57 for naturalness and lack of coloration -- at least in the midrange.