First thing you should do if you buy this computer is take out 1 RAM stick.
It has 12GB(3x4GB sticks)
This places the RAM in single channel mode and slows it down.
Simply look for the color coordinated RAM slots, find the stick that is in a slot that doesn't match one of it's partner sticks and remove it.
8 GB will be plenty for this particular system. Keep the RAM stick or sell it. Or if you absolutely need more RAM, look up the stick's part number and order one more single stick. That would be 4 equal sized sticks, and would allow the memory to still work in dual channel mode, with a capacity of 16GB total(4x4GB)