| The user manual shows it ought to work, but the effects out is PRE-boost. So, if you like boost, you won't get it at the effects-out jack.
However, digging a bit deeper, max output at that jack is claimed to be 1.5V into 100K ohms. The question is what, if any, signal loss+degradation you'll experience into a particular power amp whose impedance is less than that. It'll be amp model-specific. For example, the QSC RMX series, which is my personal preference, offers an input impedance of only 10K ohms at the unbalanced (phone plug) input. I believe that would spell trouble for the 800RB; your signal would be weak, and rolled-off in the treble region. Other power amps, i.e. ones with much higher input impedances, may be far better matches.
You could grab the signal off the direct out and send that to a power amp. I suspect that'd be a better match-up. | 
