regarding your spl question, I was playing with some rap music last night and was metering 124db at my listening position, layin on the bed, head on pillow. I think you could probably gain even more in the ideal setup, each one corner loaded, but here is what I have as far as final placement.
front left=corner loaded, front right = corner loaded, then put the other 2 under my bed with the mouths coupled together firing at wall behind headboard. I maybe losing some due to the box spring and very thick temporapedic mattress, but oh well.
I dont know if thats a fair test or what you were looking for but as far as what I know what to do, thats what I was getting, there maybe was a little more volume, but i was satisfied enough. the two under the bed, were issuing a radical deep tissue message.
if there is another way you want me to measure spl, I'd be more than happy to try.
I do know one thing, these things are mean!