i've sound deadened my entire rear deck top and bottom. still getting rattles. used to have a 15" re sx with the old school motors in there that take more power than the new ones do. i ran it at 2 ohm at 1500 watts rms and took it like a champ. i just sold the sub and my buddy is having a guy build me some custom woofers that are louder n cleaner. going to get two 12s instead in a custom box.
let me know how well your deadening works for u. mine stopped most of it but there are still some that are annoying the crap out of me. lol