Dumb Question: Add another 8gb of ram or just by 16gb kit

[MotorBoatmyGoat]

Basically what I'm asking is that can i run out and buy another 8gb kit or do i have to buy a 16gb kit?. My current motherboard is a Z87-A

 

[Tradesman1]

I'd get a 2x8GB set, there's no guarantees when mixing sets 9even if identical model #s), see item 2:

http://www.tomshardware.com/reviews/ddr-dram-myths,4155.html

 

[cdabc123]

if you already have 8 i see no reason to upgrade if you do mostly gaming