I've read, in a few different sites, that the XL-900C is 'suppose' to be a really nice sounding & quality speaker system. Copied after Yamaha's of the period, I think it was. I'd have to look that up. Maybe JBLs. One or the other.
I've been constantly watching out for a pair for at least 11 years. They never come up for sale in USA. I've only once seen one pair of 900s for sale in Japan ever. Same with the XL-700C, in Japan, only once.
Rare in USA for sure, or... the folks that have them aren't selling them.
They were made well after the Coral era.