Re: High output subwoofers.
I actually think that 12" drivers is a good idea for another reason, namely impact. These guys like to feel the impact more than extreme low frequency extension. My labsubs (witch I don't think would deliver enough output, but I have 12 of them) have gotten a lot of praise from people in the past because they have some serious impact. People call their sound "quick".
So if we're running with 12" subs, that leaves me with three choices AFAIK:
- Danley TH812. Loudest on paper, probably in real life as well. I'm still impressed by my SH50s, I have no reason to expect lesser performance from their other products.
- EAW BH760. Plenty of these around, and they are cheap. Could probably buy 12 of them for the same price as renting the Danleys. Not entirely sure about their SPL level, I've used them twice, once with 8 and once with 12 IIRC. That was loud enough to keep up with 16 KF740 and then some. But not sure if that would be an improvement over S28, the ones I use this year. On paper they have 7dB more output than the S28, and 7 less than TH812.
- Try my labs against the S28 and see how they stack up. I suspect pretty similar performance in terms of SPL.
I see a field test coming up later this summer. That's always fun 
Edit: In terms of directivity,. I don't have a stage or somewhere I can't spill low end onto. Put I prefer to keep the low end inside the audience area, this year it was roughly 30x30 meters.
