Better up front, not so much in the rear... Regardless of how low your crossover point is you can still localize the sub when it is behind you...at least I can and many others can. It feels detached from the rest of the sound stage when behind you in my opinion. I'd try for the coffee table or side/end table.
I'd think that if the sub was built into the couch you'd feel the bass much more than you'd hear it... I prefer to hear it and feel it
