I had an ancient 12" pioneer that I finally blew the surround on. I dont remember the brand of the stuff I used, but it worked pretty good - it may come apart again after a while though, but it'll keep you going while you shop around for something else. You've probably got it done by the time you read this, but I've heard not to use sillicone because some brands may eat away at the rubber (or foam more likely). I was also a little concerned about the extra weight of sillicone (if you put a lot on that is) although it might not make a difference. Just get a strong adhesive and make sure you check the label to see if it is compatible with the materials on your subs - and let us know how it turns out.