I am aware that sound cannot and will not come from a Rocket, but what can I do inexpensively to modify the sound to be maybe a little deeper and louder.
And please tell us the fool who told you this
obviously from someone who knows nothing about the Rockets, quite a few pipes for the Rocket now if you are looking for power you have CES and Viking both good looking exhaust systems now if you are after pure power and loud semi ugly pipes go the Carpenter route with no baffle.