You will net only a very small performance boost adding the extra RAM.
May I suggest that, with LGA775 at it's End-Of-Life cycle. your funds would be well-spent saving toward a LGA1155 board (the DDR3 RAM alone cost's nearly half) where even the bottom tier i3-2100 will outperform what you currently have - but would cost you the same as a better CPU.
I think thats right, building a 1155 pc with some ddr3 would be better than upgrading this one, but before doing it, I wouldnt like to leave this one on the dumps as it can run quite a lot of games and I would like to keep it so I could play with my bro as well. I noticed it struggles easy with BFBC2 but I think with the ram it will make a difference.still, It supports max 8gb, but sometimes I notice the lack of cpu(you know when the processing get cuts and slows down). I don't know how much are these cpus,Im struggling to find some of them online.
I heard that the new i5 2500k is a great upgrade from the old quads, so it must be darn fast, and the price is acceptable. I don't know if would be worth it to wait and save for longer to get the i7. Do you have any of them?