Do Ferraris normally come with a sub woofer and power amplifier in the trunk?
A factory subwoofer was an option in the modern Ferrari, perhaps it began with the 360. But as with many Ferrari options, like the Ferrari charger for example, it wasn't worth what they changed for it. Save your money and have one you like installed. Just be sure the shop knows what they are doing. Most earlier Ferraris didn't come with a radio but rather the radio was installed by the dealership.
I bought a 1996 F355 and it has a professionally installed subwoofer and amplier. the subwoofer box matches the interior of the luggage compartment. this is the seocnd car I have seen with this hardware. Obviously you cannot hear the speaker only feel its vibration.