Welcome Jim1963.
If you are worried about your Rocket being too loud you might want to start with just replacing the cat box with the bypass and then go from there. The Staintune system with their bypass provides a nice sound that is not too loud. You will pick up some power with just about every modification you make including just removing the cat box. The main reason why you would need to get a tuneboy or PCIII is to eliminate popping on deceleration. The PCIII is very good at that, the tuneboy has not come up with a surefire way to do it.
There are several examples of just about every system available in the multimedia library Link Removed