That's pretty much what I think of them, the ESL57 is limited but what it gets right, is spot on. The ESL63 is more versatile and clearly a "better" speaker if it doesn't have the magic of the 57. What I'd love to hear is the Stax F-81 which is supposed to be even better in the midrange (and even more limited elsewhere) and a fully rebuilt 57 with thinner diaphragms.