Tried the 2039 PCi and LOVED it BUT the wife said it was too big. Then ordered the PB1...it performed as advertised but it was big (it towered over my velodyne). So then the wife gave in to the cylinder and said, "I saw 3 cylinders in the picture, why don't you get the smaller one." So I ordered the 2531 PC+. I am very happy with it so far. I still have to play with the tuning (I am waiting for the wife and kid to leave me alone for an afternoon ). Ya gotta love SVS- I know I do. They have the entire sub range covered and they are still coming out with more subs!!!! SVS thank you.