The PB-4000 is kind of doing its own thing. There are subs that have higher SPL capability, however, the PB-4000 build quality and technology is just on another level. Like there is the Rythmik FV15HP, which has some performance advantage over the PB-4000 outside of the 4000's port tuning range, but the PB-4000 is built like a tank in comparison, and the Rythmik doesn't have all of the DSP features that the PB-4000 has. So you have to really compare on multiple points: cost, performance, aesthetic, features. build quality, warranty, CS, etc. The PB-4000 does very well in an average of these categories. It's a really heavy sub though.