I had some problems with voltage drop to my external hard drives. I did not notice at first that many of my SATA power cables i have bought were thin. Now i have made some with 1.5mm² cables. The thickest i have seen on ebay is 18AWG. I had to solder the crimp pin for the SATA power connector. I believe that will be good. The difficult part with hard drives is the current when they spin up. It could be up to 2.7A. When they are up to speed it is easy to get enough current.
