Wasn't really a "volume" consideration- just TOO much sub!
Granted, my HT will be acoustically better- I'm soundproofing the walls with micro board, but I suspect the second sub may be overkill. I will definitely have my CEDIA installer guy check out all placement possibilities, but who knows?
I have a family room with 5.1 surround also- so the second sub has a "home" if it doesn't work out.