Well, I thought I'd post in this thread since I have done the polyfill mod on my Klipsch 5.1 sub. I also coated the drivers with mod podge. I purchased the 5.1s from the CompUSA where I work. They were the floor model and I got them for $150. They'd been on display for a couple years I think, so I'm sure they would have crapped out by now if they had the defective amp. Plus I have a full replacement warranty on them, so if they do die on me I'll just get the Megaworks 550s or the Klipsch Ultras if we get them. Anyhow I opened up the sub by taking out the screws in the back and put about an inch of polyfill on all the interior walls of the sub with glue. I made sure not to block the port. Combined with the mod podge, my sub now sounds slightly deeper, stronger, and tighter. Of course, it's no Velodyne, but it is noticably better. The only thing I'd like to do now, is find a way to reduce the port noise at high volumes. Overall, I'm glad I did these mods. It's up to you, though if you want to take the risk. I've been using my modded sub for about a month now in 80 degree wheather with no problems whatsoever.