How do i get 3 monitors to work ?

I have 2 3870s and use 2 monitors fine.. i really want a 3rd monitor on this PC. I was told to disable crossfire.. i did but its till only shows 2 monitors. Also i thought that the new crossfireX driver made it so you could use multi monitors without disabling crossfire? Do i need 3 GPUs to use 3 monitors even though the two cards I have now have 4 monitor connections ? In other words will i need one 3780X2 and one regular 3780 to get what i need ?

technically, no. slave cards cannot be used for monitor output with crossfire enabled. 3 gpus would mean 2 cards cannot be used for output. If the third card is not linked into the crossfire, but installed, it may be possible, but you'd likely be the first to try.