Getting More Ram

[Zer0BL2]

So i am getting 8GB more ram and im having trouble deciding which one i want to get. I have a Gigabyte 970A-DS3P mobo and have two of my dimm slots filled with the ram from this link. https://www.amazon.com/gp/product/B00G9FJVSC/ref=ox_sc_act_title_1?smid=A26PVB3960EU85&th=1 

I could get two more of the same model ram but for some reason Amazon wont deliver it in 2 days with prime even though its a prime product. So i was looking at this ram at this link.

https://www.amazon.com/gp/product/B008LTJJM2/ref=ox_sc_act_title_1?smid=A26PVB3960EU85&th=1

its pretty much the same thing only difference is slightly faster timings and its 1.5v instead of 1.2v like my other ram is. (the ones i am looking at are the second option of the first link when choosing the type on amazon). Can i safely use the ram i am looking at along side my current ram? I am willing to undervolt the new ones if it means they will work fine.