Co-locating is not possible, they would be placed on either side of my entertainent center. One firing into a corner and the other firing into open space. ~5 cu ft of space on either side for dual subs.
I wish I understood how to measure this in-roon stuff, other than spl. That article makes sense as far as placement and room gain, but some was still beyond my knowledge base.
I don't want to spend more to get ~3dB that is for sure, if I am ramping up I want at least a 5-8dB in-room gain