CRJ headsets.....once and for all!!
First of all, even a brand new CRJ700 will be loud up front. There are pilots who will tell you otherwise, mostly former turboprop drivers. Don't listen to them. You need some form of noise attenuation, whether it be an ANR headset or earplugs under your normal headset.
Many people wear full size David Clark style headsets in the CRJ --- the ones they have used since they were flight instructors. Forget about it. You will have enough crap to haul around without having to find a place for a full size headset. Plus, especially on older David Clarks, the mics are extremely noisy and it drives the other guy nuts to have to listen to the hiss over the interphone. Definitely consider the quality of the mic, as this can be a major pain for the other pilot on longer legs.
I have no experience with the Telex 800 series but can recommend the 750 with earplugs. It is very light, has an excellent mic, and you have the option of sliding the pad on the other side from the mic away from your ear if you like. The earpads fold 90 degrees so the whole thing is virtually flat in your flight bag.
Some people find earplugs uncomfortable to wear with the 750, and they are if you get the cheap crappy ones punched out of a sheet of foam. I use E-A-R Taperfit plugs with the polyurethane coating. They are extremely soft and comfortable even for 2-3 hr legs.
http://www.e-a-r.com/html/products/hearing/taperfit.htm
Good luck in Denver if you will be here and be ready for those famous DEN slamdunks.