It's bad practice to mix two sticks of ram or two brands of ram or even two different kits altogether. Think of ram upgrades to be like buying a pair of shoes after you lost one out of that pair. The salesman will only allow you to buy a pair instead of one out of a pair.
If you must go for a 16GB upgrade, make sure you go for 4x4GB kit or if your board supports it, going for a 2x8GB kit. Speaking of board's supporting it, Mind sharing your full system's specs like so:
CPU: AMD FX-8350 4.0 GHZ
Motherboard: Gigabyte GA-78LMT
Ram: XPG ADATA 1x8 8GB 1600Mhz
SSD/HDD: 1TB (not sure of brand), 120GB SSD (also not sure of brand)
GPU: GTX 1060 3GB
PSU: 500W
Chassis::https://www.amazon.com/SkyTech-AMD-1060-I-Desktop-Gaming-Computer/dp/B01LAJ52RA/ref=sr_1_1?ie=UTF8&qid=1502153922&sr=8-1&keywords=skytech+shadow+1060
OS: Windows 10
Even though you can't use them together, for the sake of relevance, can you pass on a link to both varying ram ktis?