I am running a Boston Accoustic G5-10 sub w/ 440wrms running to it, and my rattle is minimal. The main rattle source (that is audible from the cabin) is the rear decklid, but that can be tightened up with a little weatherstripping. I would recommend dynomatting the trunk (although I have yet to get around to doing it myself....I am a bit of a slacker as of late ).

John