Of all the analog xovers I've seen, only the Pass and Krell seem to be internally balanced, and I'm not 100% sure about even those. Most that do offer XLR input/outputs are "servo" or transformer balanced, including Bryston, Marchand and all the pro gear. For my purposes, the servo-balanced NHT X2 was fine, but it's more for subs.
Didn't find any direct info on the FR's and the only crossover number I found for any Apogee was 700 Hz, with no clue of the slope. Maybe you can test them with a calibrated microphone and a RTA, like HolmImpulse, to find out. Caution: With wide-range planar/ribbon drivers, there's also a good chance of notch filters far beyond the crossover point.
Unrelated but did stumble across some opinion you might find interesting...
http://www.high-endaudio.com/RC-Amplifiers.html#Mark
Didn't find any direct info on the FR's and the only crossover number I found for any Apogee was 700 Hz, with no clue of the slope. Maybe you can test them with a calibrated microphone and a RTA, like HolmImpulse, to find out. Caution: With wide-range planar/ribbon drivers, there's also a good chance of notch filters far beyond the crossover point.
Unrelated but did stumble across some opinion you might find interesting...
http://www.high-endaudio.com/RC-Amplifiers.html#Mark