If you're talking about adding 16GB to your current 8GB stick, I'd say you would be better off buying a 16GB (2x 8GB) kit of HyperX Fury RAM and not using your existing stick of RAM. I don't know what you are using your PC for but I doubt you need 24GB of RAM.
As the thread mentioned, even the same model of RAM can have compatibility issues when they are from two different kits. If you want 16GB of RAM, buy a 16GB kit not two individual 8GB sticks.
If you want to just buy 1 stick of RAM to add to your existing 8GB stick, try and buy the same model to minimise your chances of getting any issues.