I used to own two passives galaxy hot spots.
And I once borrowed a powered hot spot (PA5XD) to try exactly what you are describing.
It was for a loud outdoor concert that was to be recorded from the board for a CD.
I had played there before and had a real problem with hearing myself, and the sound guys sent the bass back at me in a wedge and of course there was feedback.
The powered hot spot worked fine as a pitch reference but as smogg points out there was no low end. But the was fine I just wanted to hear myself so could play in tune and not be embarrassed by the CD. The best part is the DAT off the board disappeared.
I think those passive hot spots are 16 OHMS, don't know if that is going to work with your GK 800RB. I used to use the two I had at an Italian restaurant duo gig and they worked fine for 'just a bit of help' amplification. Plus the were almost invisable. But for monitor use I think a powered one would be the ticket as you would have more control over tone and volume and just run it off a line out or something. Maybe you can find one to borrow. They also have a new powered micro spot. http://www.galaxyaudio.com/galaxy/ga...S.html#HOTSPOT