My initial take was to leave my 25-31 PC (serial # 000003) as is since it pessureized my room to insane levels with clean musical bass, so what is the point of upgrading ? Then I saw side by side pics of the driver, and I had to have that big ass magnet whether I needed it or not. After removing the old driver, I A/B ed the drivers in free air with bassy music and there is a obveous difference, esp at loud volume. The driver comes with excellent instructions, but I still managed to mess it up. Put everything together- no sound at all. Turns out I fed a little too much wire into one of the spring clips so it was biting on insulation instead of metal. So there is a gotcha to avoid. And heed the warning about making the driver screws too tight- I think I nearly stripped a couple. I was a fence sitter and almost passed on the upgrade, Glad I didn't. This is a real upgrade. The sub is actually more musical and sweet sounding.