I went from the CRJ to the Q400 and used my Telex 850s. They work great. The noise level in the front of the Q400 is comparable to the CRJ-700, just a little hum from the props. The loudest thing up there is wind noise from the windshield wipers and sometimes the side air vents. It can be kind of hard to hear if you have the side vents full open or full closed but somewhere in the middle works pretty well. If the cabin noise reduction fails in flight you will notice it right away but it's still comfortable whether or not it works. It still has the same problem all Telex headsets do that if you leave the hot mic on it creates static for those with really quiet headsets although it is no where near as bad as it is on the CRJ.

If you can tolerate the noise in the 700 with the 850s I don't think the Q will be a problem.