I know i've had HPET enabled the whole time and used both those flags with a 560ti but it didn't help me unfortunately.
Here's an update. I installed the latest bios for my board, 2.20 and now i can get to the installer with the flag PCIRootUID=0. I can't install as i'm waiting on a new SSD, should be here anytime. At least i'm over the original hurdle of the rebooting at Starting Darwin. I'm not saying updating your bios is the answer for everyone but it works for me.