Brian, I'd agree that the biggest improvement over what you have now would result from getting the VP160. If you want to spend what you mentioned you could also add a second PB12-NSD, which properly positioned(e.g., midpoints of opposite side walls, front and back walls or diagonally opposite corners)would give you both stronger and smoother bass. I'd think that there would be relatively little reason with those subs to go with M80s; the M22s should continue to be fine.

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Enjoy the music, not the equipment.