I can report that the Rockford Fosgate P3SD2-8 fits in the stock enclosure if you use a 3/4" MDF spacer. Screw the spacer down with the stock holes, then screw the new woofer to the spacer. Don't forget to plug or cover the hole in the back of the enclosure. I used 3 inch 12 gauge speaker wire from the stock connectors to the Punch's push terminals and wrapped the connections in duct tape. I had also stuffed the box with polyfill previously. Completely reversible mod, if you want to put it all back to stock.
The woofer is DVC 2 ohm so its a direct replacement load-wise for the Sony speaker. It also kicks the
out of the stock woofer. I turned my bass down to +1 from +4 and still have more low end response. The bass is more vibratory, if that makes sense. Whereas the Sony is boomy and sort of clipped, the Punch goes more into subsonics. My dubstep (yes, I know) sounds like my home stereo now. I feel the music as much as I hear it.
I listen to everything but Country (and even then a little Soggy Bottom Boys) and the Punch makes everything sound better. It helps that I don't have to boost the bass so much, of course, but the Sony was too loud in the 45-55Hz tone and it overpowered the sound. I've had polyfill for about 4 months, and I tried running with the center unplugged for about a month. Each one of those moves made the Sony sound a bit better, but I still wouldn't call it close to the Punch.
The Punch can be had for about $100 on Amazon