I ordered the PinWoofer backbox sound kit and installed it yesterday in my POTC. I have an external sub and wanted the mid range speaker and the tweeter in the backbox to improve and get to the sound level of the sub. My expectations were high and have been more than fulfilled. The sound from the backbox now is brilliant, chrystal clear and very transparent. It is so dynamic that you have to level the volume of the kit down a bit, when you increase the general volume of the pin.
Special thanks to Dan from PinWoofer, who contributed a perfect service for all questions I had. Respond times were incredibly fast.
So highly recommended.