Your most probably not running the cards with the most up to date kexts or something, on my installation my graphics are stuck in the same resolution even with the corret kexts, but as soon as I use gfx strings, everything is up and running!!!! Try dowloading and running osx86tools and use their built in gfx editor to add your cards strings (not sure if any of your cards are supported, would check but I messed up my installation lol, so reinstalling now)