that thing about the the subs in winter is a good question. I found out the the reason why one of mine broke was the wire lead to the magnet broke off the wire from the connection terminal.
I have two 12" JBLs and I have the center reflector on my Mystique rattle, and I think the plate does also. I also beleive I have seen the rear deck shake at times. So I think you either live with it or you dynamat everything to eliminate the sounds
