I tried to pad the inside of my subwoofer (Z-560) once with polyfil in hopes of cleaning up the bass a little (didn't work). I also unscrewed all 50 screws only to find that this wasn't the way into the box! Doh! Why do they use so many screws?
What you have to do is remove the grill. I used a wire to pull the grill up and off, a small reg. screwdriver also helps from the sides. Then there are only like 5 or 6 screws from there - it's easy to figure it out once the grill is removed! Good luck!
-VTrider