Installed 10.9.2 as a new install on a Gigabyte GA-EP45-UD3P using a Chameleon-based installer and no DSDT. Everything works fine.
The Sapphire AMD 4870 512MB has worked perfectly from the start (on one monitor) with QE/CI but had no dual monitor support. Using DVI to HDMI adapters to feed the two 1920x1200 HDMI displays.
To try to get monitor #2 to work, I installed "QE/CI Exotic Patch for Mavericks 10.9.2" by Sascha_77 from this forum. Am able to see boot up text on both monitors during boot. I can use the "Gather Monitors" from OS X System Preferences to "arrange", but monitor 2 never lights up (other that during the boot process).
I'm using the main x16 slot and PEG setting in the BIOS.
I haven't seen definitive success with dual displays as a result of any googling.
Graphics/Displays system info screen capture is attached.