Well, is there real difference between FX and GX? I mean you culd just disable IGP and have the FX, couldn't you?

You can even try to turn on SurroundView if they still have it in BIOS and try to have 4 displays...I succesfully used this with my 780G+HD 3870, half year before any mention about Eyefinity (well, there were some driver issues with some Catalyst versions and I never tried any game with this, but it could be just matter of settings as multiple display gaming was possible before Eyefinity, only more complicated).