Take out the resonator and you presumably get a sh*tload of noise. If the box you mention is indeed a resonator then its main function is to reduce noise levels. They apparently have a specific volume of air and length which are calculated so that the sound waves reflected in the resonator help cancel out certain frequencies of sound in the exhaust. First check it is a resonator and if so I'd be tempted to keep it for the timebeing and concentrate on the other boxes. I want to do this one my V6 too. Most countries have legal noise levels and I have seen plenty of people stopped by cops for having big bores.
Cheers Justin, don't really want it much louder, already has a Supersprint rear box which makes all the right noises. Perhaps a two piece replacement pipe might be the way to go in case its too loud without wink