Hmm, those are interesting speakers... Oddly, the similar but smaller Starlet 4
doesn't need separate amps. I'm guessing the big ribbons on the Starlet 6 simply make a difficult load, impedance-wise, and most amps can't handle them plus the woofers at once. I have a feeling that an M200 might be tough enough, but not sure.
Usually the internal crossover deals with level-matching between tweets and woofs. Sometimes it's selectable for personal taste, but requiring amps to do so is unusual.
You might take a look at pro amps.
QSC is one such that provides amps with variable gain controls. I'm sure there's others.
In my system, the active crossover (a Behringer DCX2496) also provides selectable level matching, among other things.
There are ways to do it. Cool speakers!