So I was able to solve this by re-installing 10.9.1 from scratch. Previously, I installed 10.9.0 and updated to 10.9.1. Anyways:
1. Created new 10.9.1 USB stick using fresh 10.9.1 app from App Store
2. BIOS (version F4): Load Optimal Defaults, Set RAM Profile to XMP 1 (DDR 1600), Disable VT-d, set boot to P0: SSD (not UEFI), disabled all other boot devices -- nothing else
3. Install fresh 10.9.1 from USB stick
4. Reboot
5. Install Multibeast (see attachment)
6. Done
No need to install USB3 driver as the native appears to work fine.
Also, I'm using the top HDMI port.