A different angle...
With all the speakers reproducing full range bass, woofers are in many places in the room. Standing waves and cancellations you didn't plan on may become evident. With all the bass coming from one location (the Sub) it's possible more locations in the room would sound better (instead of one sweet spot) Experimentation may bear this out. If all your speakers are indeed capable of reproducing down to 20Hz it could very well be an issue. It's even tricky with multiple subwoofers.
Rich.
With all the speakers reproducing full range bass, woofers are in many places in the room. Standing waves and cancellations you didn't plan on may become evident. With all the bass coming from one location (the Sub) it's possible more locations in the room would sound better (instead of one sweet spot) Experimentation may bear this out. If all your speakers are indeed capable of reproducing down to 20Hz it could very well be an issue. It's even tricky with multiple subwoofers.
Rich.