Elliot, To me, an output of 300mV is not "line level", which is why I ask my question. It is possible, if not probable, that the built in amplifiers in these small self-powered speakers are very sensitive so as to be driven by a signal at 300mV. That's likely the answer to my own question.
In a Youtube search, I found this video, which looks good for my "client". I am fairly sure I saw Fluance products for sale in Tokyo, and I am certain that iFi Zen is available there. Maybe this is my solution.