Well, I hadn't originally contacted Millersound because their website strongly discourages you from getting in touch about brands that are not listed, but, as pointed out above, they do list SEAS. So I emailed, and they in fact think that they would be able to repair these.
I'll have to figure out how to remove the woofers, which scares the hell out of me, but I'd be thrilled if I could in fact get the whole thing working again.
I confess to being exhausted by this project, but....
Will update. Thanks for the suggestions!