I too came to the CRJ from King Airs and B1900s so initially I used the Bose X I had but soon realized it was overkill. It takes up a bunch of room in your flight kit and really provides way more noise canceling than you need. The CRJs aren't really any louder than the older 737s. Infact. I opted for the Telex 850 and could not be happier. It is very small but provides a good amount of noise canceling with great sound quality. If you get the 750 you will most likely end up wearing ear plugs underneath it. Not really a big deal, just kind of a pain in butt.
The bose QC is nice, but again its large and way more noise canceling than you need. I can see the appeal for commuters, but I'm happy using my Ipod headphones during my commute. Also, they are much easier to conceal from FAs when you just want to finish that song after they make the "no electronics" announcement.