Also to help keep rattling down, tune the amp correctly. I found this lowers distortion and excursion and helps not "jiggle" everything in the cab. This I how I do it.
Put in a 100hz test tone and unplug all of your rca's cept your sub. turn everything to flat and 0 on h/u and amp. turn up cd player to 3/4 volume. take how much power is going to your sub at what ohms and multiply them, then take the square root. EX: my amp does 300x1 at 2ohms, so 300x2= 600, then take the square root and it should be like 24 or so. Do that for your amp. Then hook up a digital multimeter on your outputs to the sub from the amp. Turn up the gain until you hit the # you got when you did the math, in my case I would turn it up until I hit 24v. then your gains are set and your sub is getting full clean power that will help reduce extra distortion and rattles.