It has to be said that they ARE loud but not the loudest. If you ride sensibly in built-up areas you probably won't piss off too many people. If you always accelerate hard then expect to get booked!!! I had a set of Big City Thunder baffles fitted, part no. QQ1845, which cost me US$170 landed via:
http://www.bigcitythunder.com/pages/product-fit.html
They knock off about 10% of the harshness and outright volume but still are quite loud.
They really are the coolest looking (mainstream) pipes available!
Go for it. You'll love'em!