Hi,
Going back to the original question, I have a 6tb WD Red in my MED1000X3D to play my 3D ISO's and it plays perfectly. My network struggled with the bit rate required for 3D ISOs. I also have a Synology DS415+ for the rest of my media; again no issues. Prior to investing in a NAS, I did have 4 x 4tb WD external HDD's connected to a hub. The 1000X3D was able to read all the drives via the usb port; again with no issues. The only reason I moved from this configuration was because I wanted to network my entire house.