I've heard the opposite. That x-pipes make a little more noise I'm not sure, I've never owned one so this will be my first.
Talk to the Hand. Jim Hand, that is. His book has a comprehensive list of muffler setups with dB for with and without X-pipe. Every source I've read says the X-pipe quieter. It makes sense that it would be too, because with each exhaust pulse splitting between two mufflers you've increase your effective muffler volume.
