Carp, this is spectacular overkill!
As to a few comments made, I completely agree with FOH about the colocation not being an issue for summing the output of all 8 drivers. You should be capable of well above reference at every frequency, only limited by your signal chain's roll off.
I would also think that each box is going to be roughly about 75% the output of a SubM HP (total guesstimate based on displacement), assuming proper amplification. Plus, the SubM has a 7hz HPF, which you won't have. As FOH said, 2 of these boxes would likely get you reference for all but the absolute lowest frequencies, and 8 will be significantly over.
Personally, if at all possible, I think 4 would be perfect when placed on 3 walls like PeteW did
. Obviously, each room is different, but that centered-on-3-walls approach showed spectacular results. Check out the three posts following that link and see what the final response was without any EQ. Still wanting to get his miniDSP back in the chain to apply an LT for 3-10hz...someday.
Edit: looking further at your pics, it appears that one on either side of the center channel, and one directly underneath your SL & SR channels would fit, maybe working towards the slightly-modified Geddes approach (I think that's it) mentioned above, and give you the nearfield tactile response so many here talk about.Edited by nube - 3/5/13 at 10:55am