Upgrading my RAM, better to add, or replace?

[Dhakos]

I currently have 2 x 4GB sticks to equal 8GB but I want to upgrade to 16GB total. Initially I was going to buy the same 2 x 4GB sticks again since I have 2 RAM slots spare, but then I read about dual channel/quad channel etc and basically want to know if it would be better to add 2 more 4 GB sticks, or buy 2 x new 8GB sticks. Thinking performance wise, the price isn't too different.
I have MSI Z77A-GD55 mobo, and my RAM is Kingston 8GB 1600MHz DDR3

Thanks in advance for advice

 

[nickc]

For DDR3 there is no quad channel, either way would work fine, go for the cheaper.

 

[Route44]

Why do you need 16 gigs of RAM? Are you rendering video or doing graphic design?

 

[Dhakos]

Rendering video yeah, that and I have A LOT open at any given time

 

[Route44]

Then that would make sense.