Here are some great headphones used commonly for location sound recording in film and video
http://www.circuitcity.com/ccd/produ...T&cm_keycode=4
Your best bet is to make your EQ adjustments while listening on a good pair of speakers.
There are folks that use $60,000 studio monitors and still have to check their mixes on other speakers just to be sure it translates well from system to system.
Mixing on any headphones is basically a no-no but if you get good mic positions and maybe use a high pass filter or low freq. roll off, you should get something pretty usable.
Sorry if I missed it, but what are you planning to use these recordings for?
Just so musicians can use them for reference? For all who enjoyed the music? Sales?
How big is the choir/ensemble?
Are you using the preamp in the SB card?
What model Behringer is it?
Once I know more about the specifics, I can help you more.
I teach audio engineering and design rigs for all applications.
Sorry for all the questions but no 2 recording situations are alike so you must tailor the process and use of gear to each situation.