Been following a few different GPU threads here and other places, and it seems like the R9 280X 3GB VRAM version is the most powerful AMD GPU that will run in the cMP. One of the EFI geniuses at Netkas even wrote an EFI for it that will enable boot screens. For many of us still keen on running cMPs for years to come, the 6GB version of the R9 280X seems to be the holy grail of aftermarket GPUs. (Assuming that official Mac Versions of either Nvidia or AMD GPUS will not be updated again due to the nMP design). In addition to just being a beastly, beefy GPU with a ridiculous amount of VRAM, it has two 6 pin power connections, so if the leaked specs are correct, than it will run reliably within the limits of the cMP power supply. Pertinent links: http://www.tomshardware.com/news/msi-radeon-r9-290x-280x,25632.html http://www.hardware-360.com/msi-prepping-two-new-amd-graphics-cards-for-ces/ The purpose of this thread is to collect and consolidate any information on the R9 280X 6GB model - that's the 6GB version, NOT the 3GB model - in hopes of enabling PCIe V.2 link speeds and any EFI/rom (sorry I still don't quite comprehend the difference between EFI and rom) that will allow boot screens under OS X. Thanks much for reading and for any info you might have to share!