I would delete any screen/Monitor sections past Screen1 and also delete them in the server layout section.
If you look closely reason why you got 6 of each is because it gave you "other" driver options for both devices "fbdev,vesa" plus the two radeon sections so thats 2x3 = 6.
With that said comment out the other driver sections or delete them. (I say comment out because if you may want to try to use those drivers one of other drivers later might get you going)
Than you should be able to use the config file without getting that error.
Like this: http://openpaste.org/1d419D44