The amps for the system's woofers are bolted to the back of the speakers...
these are little more than 25 watt booster amps. The dash coaxials and rear
tweeters are powered by the head unit directly, though the dash coaxes may
also have a woofer amp on them (if not it'll be a crossover only - been a
while and I don't remember when they stopped putting the amp on the dash
coaxes).