I've been reading this conversation and I have a comment. But let me say I have some rock experience playing out, not a ton. None in very large venues.
I thought the point of the Kone, powered or not, was to serve two main functions. There maybe more, these two stick out.
1. Practice in a jam session or bedroom with great sound
2. Act as a monitor for guitar player in a large or louder session while the KPA feeds front of house.
I would never expect a 12" speaker fed by a solid state box to accommodate anything much bigger than a medium sized bar type venue. Of course nobody is going to mic a Kone cab, that's why we have the KPA in the first place, to either feed a Kone, or PA or both. I wouldn't consider buying multiple Kones, it seems redundant and unnecessary.
So am I thinking correctly here or what?
If you can't hear yourself at practice in a metal band why not just feed the KPA into the mains with the vocalist? You don't have to put it all in, just enough.