I would visit;
and let it scan your system. They will tell you which RAM your system can take.
But if your question is whether your system 'needs' more RAM, then we can't say. 5GB seems good to me. Are you maxing out on RAM at all?
I would like to know what is the best ram or memory cards to buy, it has 5gig ram now, 2-2gigs of ram and then 1 gig of ram DDR3 SDRAM - non-ECC
4 DIMM (240-pin, DDR3). Should I leave the ram in it and buy just more ram? Can I buy like two 4 gig ram and put in with these? It has two slots open. What is the best way to go and what is the best ram for the price? any ideas?