I don't know about the Gen 2 duals, but I'll assume they run the same muffler with the singles on the other generations and I can comment on those. They're definitely not what I'd consider overly loud in the single format. Certainly not compared to known ear shattering models like an M4 GP or an Austin Racing etc. They're louder than a Yoshimura of course.
If you want louder from a Danmoto muffler, it's easily shortened with a hacksaw and a rivet gun.