Can i add 2x8GB ram to a dual channel motherboard with 2x4Gb?

[Pieninja]

I am using a computer with a dual channel G.Skill Ares F3-1600C9D-8GAO 8GB (2x4GB) DDR3 ram which i have no trouble with when playing games however it is slow when rendering projects in Maya. If i were to buy buy more ram, would it be possible to add 2x8Gb chips or better to just add another 2x4gb ones?
I would like to have as much ram as possible but i cant afford much due to paying for university, textbooks, etc.
What would be the best course of action here as i do not have the time to render my projects to the quality i would like with the amount of ram i have?

 

[webpro2k02]

The rule for Dual channel to work is to have just a pair of memory modules to be of same specs, so you are good to go with 2 x 8GB identical pairs, with existing pair of 2x4GB.

 

[Pieninja]

Best answer selected by Pieninja.