I plan on installing a 100W siren speaker designed for Police/Fire on my truck. in addition a siren control unit for the electronic air horn and PA function. more expensive. but louder and proven durable. plus the speakers are more compact.
Warning: this may and probably is illegal to install a siren system in your vehicle in your area and or areas you travel to. please look into the possible legal situations that may arise from installation of such products.
another downside with this is this adds another electronic device and another microphone on top of your HAM/CB unit.