I have a set installed along with the V&H Power Dual header. V&H is a high quality manufacturer, the chrome is first rate and the fitment and instructions are clear and complete. The Hi-Output slips-ons are not "loud", but it is hard to quantify a sound in writing. They are louder than stock, about the same as the Rinehart's I had on my 2006 SG, but not so loud that I can't enjoy my music and not so loud that I need ear plugs if I ride all day on the highway.
If you want to piss off the neighbors, they are not loud enough. If you want to piss off your BSR they are not loud enough. But for me, they are loud enough, and I like the look, the chrome, and the V&H logo that sticks out past the bags. This will "date" me, but when I was a kid I wrenched a set of "glass pacs" on an old Chevy (my first car) they sound like that.
OWL