Memory Upgrade recommendations

[Zzenith]

I currently have an older

Gigabyte Z68XP-UD4 (Socket 1155) motherboard

Which 8gb in dual configuration.

Could someone please advise me on increasing this to 16gb, would it be best to buy 2 x 8gb sticks or another 2 x 4gb sticks. What will give best performance.

Would be most grateful if someone could spec me some quality suitable memory.

Thanks

 

[Zzenith]

Thanks for the help, much appreciated