Currently I'm running a Gigabyte GA-Z77X-D3H motherboard, with 8Gb of Samsung Green DDR3 1600MHz memory. Just thinking of upgrading the memory to 16Gb, as I think I'm starting to hit the RAM limits bit during gaming (Battlefield 1), and also it just feels like its time to have an upgrade! 
Would it be better to buy another 8Gb memory, or ditch the memory I have and buy 16Gb new?

Would it be better to buy another 8Gb memory, or ditch the memory I have and buy 16Gb new?