Hi, this is the common mistake everyone does. Even I made the same mistake. There is a reason why RAM sticks are sold in packs of 2s or 4s etc.. It is not generally suggested that you just add new ram sticks to the existing one even if you get the Speed, timings, voltage, and version numbers are exactly the same. People did get very very lucky (rarely) and mixed kits might have worked for them. As I said, this is not suggested for just regular install and forget situations and definitely a NO for overclocking (if you do not know what even setting in the RAM section of BIOS does and you can tweak it to the degree). Each stick in a RAM kit has been tested and modified(if needed but rare) to match and become a kit that is absolutely compatible bundle of RAM sticks. So, I would suggest you flip your existing RAM and get a kit that is 2X16 (duel channel) as your CPU only supports dual channel. I said 2X16 if you want better overclocking if not you can go for 4X8 kit which still works in dual channel but overclocking would be a bit hard.
Hope this helps. By the way, I would suggest you understand the frequency and timings relation for RAM and how it affects the performance before you rush to buy a kit with high frequency.
