Hey, I currently have a GTX 780 (Asus reference model IIRC) installed. It is chilling in there for almost 2 years now I'd say. Back then, I used two of the HDD bays to safely power the card with two additional SATA to PCIe cables, as the 780 has a TDP of 250W. Now I am quite in the need of these HDD bays. I searched around again, and appereantly, it seems quite safe to just hook the card up to the logic board with the 6 and 8 pin cables. MacVidCards also DOES NOT list the card under his "These cards pretty much need an external PSU" list. However, he does list the 780 TI. BUT, according to the nVidia site, the 780 TI also has a TDP of 250W. Then again, I've seen people using overclocked EVGA 780 TI models on just the logic board connectors, and not having troubles at all. TLDR: I suppose it is safe to hook up my GTX 780 (3GB) to just the internal logic board 6 and 8 pin connectors, and not waste 2 HDD slots? I do have a dual core 4,1 (upgraded to 5,1), in case that matters.