I have tested all 3 regarding the sound. haven't been on the dyno to way which one generates most power.
in my opinion, the devil double has the best (not the loudest sound). Akrapovic with DB Eater is not much louder than a Stock 450 2005. Without, it's crazy loud, imo it's too loud. Arrow is ok, i have different DB-Killers for it so i can adjust how loud it is.
Husqvarna SM 510 R '06 " Eddy Seel" -> Sold
Husqvarna SM 450 R '04 -> Sold
Husqvarna SM450R = sounds like thunder , strikes like lightning