The Bose is a great headset, but headsets that rely so heavily on electronic "active" noise reduction don't really do that much to physically protect your hearing. I used the A20 when I was flight instructing, but didn't find it to work that well in the Q400. It was quiet enough, but I got a lot of feedback from the intercom system, and could hear bleed-through from the FA's talking on the phone in back. That got very annoying very quickly.

Personally, I'd consider an in-ear headset like the Clarity Aloft. I have the TSO Clarity Aloft and got custom earmolds made for it by an audiologist. It works great in the Q400, and I assume would do equally well in an RJ.