External riser for GTX 750 Ti, powered or unpowered?

[@msteramned]

Hi Guys,

Just got a Gainward GTX 750 Ti that's chugging along nicely at 300kh/s with very little tweaking. I was just thinking that since my mobo (MSI PHA-67 C43) has 3 additional PCi x1 slots I could just run out ribbon or USB3 cables thru the rear of the case and run another 2 or 3 GTX 750 Ti's externally. Question is since the cards don't have external power (power comes from PCI slot) am I correct in presuming I would need to use powered risers and not unpowered risers?

Just wanted to be sure it will work before dropping the money on the cards. Thanks for your help.