are you sure that the game supports crossfire ? most of the games doesn't support crossfire or even if they do support crossfire you still have a lot of work to do or you'll end up not loving your crossfire setup.
here is the website of radeon pro : http://www.radeonpro.info/en-US/
if you will kindly check my posts regarding my 6850 "everyone told me it wont run very good on 1080p" but im not having problems even with crysis2 with all max settings @ 40-45 fps by using radeon pro tool. i got a friend who's running 6850 crossfire without radeon pro on games like d3/crysis2/nfs the run and more the fps rate is really bad.