1300 or 1600

Hi Guys im new here...i have a urgent question, i have a Dell Optiplex 790DT. my specs are: psu:550w Gpu:(GalaX) Nvidia GeForce GT 1030 low profile cpu: intel core i3 2130 3.40ghz So now i actually have 4gb (2x2gb)RAM installed and im planing to upgrade it to 8gb. My question is, if i buy 2...