Hi Malice,
The PB12nsd is tuned a bit under 20hz...so it will dig a little deeper than the Plus/2 in 20hz mode. The plus/2 will have a big advantage in output capabilities of course. But if you never/rarely push the PB12nsd very hard...the benefits of that could be debatable..
Does the room have any large openings to other areas of the home? Also, have you calibrated the system with a meter? If so, how close to reference level do you push action oriented DVDs (with your loudest listening levels)?
Tom V.
SVS