The documentation says that the power amp output is internally parallelled to the Monitor Output, presumably so that one could set up a stereo pair of guitar / FRFR cabs with the appropriate output settings.
I note that when using a powered stage monitor off the Monitor Output, turning off the internal power amp results in a large drop in output volume from the Monitor Output. This can be compensated for by just increasing the volume on the powered stage monitor (or by increasing the volume of the Monitor Output in the Output section, presumably, although I have not tried it).
All this confuses me a little as the documentation has a very strict warning about not connecting powered devices to the Speaker Output jack, but the Monitor Output jack doesn't care. I guess they're buffered differently...?
I don't need to keep the power amp on as I'm not using a guitar cab, so other than the resultant power drop at the Monitor Output, is there anything else I need to attend to for my powered stage monitor?