Do you have single stick of ram or 2?
Most people don't need much more than 8Gb of ram but you could probably benefit from it since you have an APU.
It looks like that MoBo only has 2 dimm slots so you're probably going to be looking for an 16Gb kit in 1866Mhz
http://www.newegg.com/Product/Product.aspx?Item=N82E16820231615
This is a good example. I have 8Gb of 1866Mhz GSkill in my PC right now and it's great ram. Will easily OC to 2133Mhz too if you want to try it. The APU can benefit from the faster ram speeds.