From what I see they would both run at 1.35V and are compatible with quad channel as well as XMP. The only thing that there would be is a height difference in the ram. Even though mixing RAM is not a great idea... You have the same speed and same brand just barely a difference in models, I think you'll be fine in this instance.
Fury Height:
34.1mm
Predator Height:
42.2mm
You could always play the safe part and buy a 16GB (2x4 or 4x4) kit from another brand and keep the 8GB you have in the machine and save it for a rainy day or another build.
Keep in mind if you decide to do this or get a 16GB quad channel kit, your hands will be tied with future upgrades to 32 or 64GB.