Ok, I got the card working with some caveats.
Note that this is all on OS X 10.10 Yosemite, because Mavericks does not have the new AMD8000Controller kext to support Bonaire.
I needed to patch the Baladi fb, obviously not the best choice for a laptop with nothing but display port outputs, but it was possible, eventually.
With this patch, I can use the internal screen with absolutely no trouble, sometimes. Other times, it will boot to a gray screen. I need to boot again and again until it will work, at which point it works perfectly with CI QE and all that.
My clover patch:
You may notice that I passed a very odd value for the encoder, 6, which according to documentation doesn't exist. Me trying this is the only thing that allowed my screen to have proper colors without any screen tearing. No idea why, but it works.
Here is where I have issues:
1. I cannot use more than one display at a time. I can set up the frame buffer so I can use an external display port monitor. However, if I plug in a display port monitor while using the internal screen, it freezes. Apparently this is a limitation of OS X's support for newer AMD cards. If anyone knows a way to support multiple monitors, my docking station and I will thank you profusely!
2. Sometimes I cannot get graphics working and it stalls at a gray screen. I'm pretty sure this has something to do with issue #1, though.
3. Sleep works, but resume doesn't. I have yet to patch my DSDT, so this could be why.
4. I haven't been able to recreate my success in Mavericks yet, but I will try later.
Anyway, I think I might be the first person to get a Saturn XT card working, so I'm kind of happy. But if someone can improve this situation, I'll be happier!