Without knowing the make and model of your MOBO it would be impossible for me to tell you if you could keep your existing Ram. I will be happy to check for you if you would like. I would need you to do the following and that will give me the needed information to make a knowledgeable suggestion for you.
Download and install EVEREST
1: In left pane expand Computer folder.
2: Click once on Summary
3: In upper menu, go Report
4: And then to Quick Report-Summary
5: Save it in text file, and paste it in your next post.
PLEASE DO NOT INCLUDE ANYTHING UNDER THE LINE THAT SAYS "DEBUG- PCI"