Hi James,
Thanks for the details of yours...
Regarding the loudspeaker, I just wonder if a (later) replacement loudspeaker was tried as a cure for your weak bass problem? Just a thought. With a really careful look, you might be able to spot clues - perhaps very small dents in the woodwork where those metal brackets were pressing against a slightly different spot previously?
Of course, it is possible that yours left the factory that way, but the earliest gold loudspeaker that I have on record is 33518. Though having said that, I do have 4 other sets in the "odd ones" section with a gold Elac, but there's every chance the loudspeakers are replacements. They do fail occasionally.
Anyway, thanks again, and enjoy the set
Mark