The Sennheiser was a great headset -- but not for the CRJ. Its important to remember that ANR technology has not advanced to the point yet where it can cancel high-frequency noise. It works in the low frequency range. It does a terrific job getting rid of engine noise etc... but doesn't do much at all for wind noise, air-conditioning noise, etc.
Those, unfortunately, were the big noise-makers in the CRJ cockpit.
So when I had my Sennheisers, I was using both earplugs and the headsets to get the sound down to a reasonable level.
The CRJ cockpit is very loud for a jet-aircraft. I would recommend an ANR headset which also employs PASSIVE protection i/e covers the ear. Telex and Dave Clark make good models of those as do lightspeed and even Marv Golden.
Obviously the best of the best is the Bose X. Bose has a deal where they'll put $100/month on your credit card interest free. That way you dont have to plunk down the $1000 all at once.
Dont take my word for it though. Next time you're in Cincinnati, drive over to Sporty's Pilot Shop in Clermont County. They'll take out all of the ANR headsets and hook them up to a test-bench so you can try each one of them.
The Bose worked great for me in the CRJ and it works like a DREAM in the Learjet. They're lightweight, comfortable, and -- best of all -- I have no worries about hearing damage as a result of airplane noise.
I only wish I had them back in the 90's when I was sitting between the Garrett sisters in the J31.