Gtx780 + mp 3,1 / 5,1

[SDAVE]

Just got a modded GTX780, will it work ok in my 3,1? I plan to get a 5,1 (looking for a good deal at the moment) and then upgrade the CPUs down the line. I wanted the trashcan but I really need CUDA right now and the 5,1 with GTX780 is a cheaper upgrade than the base trashcan.

Also since the GTX780 is modded, which cables should I use? Should I use the SATA to 6pin?

Cheers guys