I don't think the whole idea is to make it "so loud everyone can hear me coming down the block". Why would you even want that? Have you seen the new South Park episode titles "The F word"? I highly suggest you watch it just to get a good idea of what the townspeople will be calling you.
All joking aside, like everyone suggested, you can get headers, downpipe, test pipe, cat back, larger diameter tubing, etc etc... but you really don't want to overdue it. Getting rid of all your back pressure is going to hinder your performance.