I would go with the 2x8GB unless you found some 2x4GB kits on sale for a really good price you could get two of. Honestly there is not much difference between the two. If you are a heavy overclocker it would be best not to use all 4 dimms. Getting 2x8GB now allows for easier upgrading if you ever need more than 16GB, but that is unlikely unless you do some serious editing and/or design.