it depends on the specific equipment in question...the easy one- amps are a gamble..... many times, i've had the caps explode from sheer cold (this also takes the battery out with it in most cases) as for the sub, well, rubber/butyl surrounds can turn rock solid in sub-zero, and just get stiff in freezing. usually a warm-up of both the vehicle and sub will loosen them up, but if the sub is not moving, the coil isn't cooling, and then there is the stress induced by stiff components. it is most common to see different types of foam surrounds also crack and split predominantly in the cold, not to say they wouldn't normally wear out and crack with time, just more so in the cold. only things i take the systems out of for the winter is my toys not driven then, mainly to prevent theift, other than that, i judge the sub, and warm up accordingly.