Both my box and my laptop have 4GB of DDR3. I game, and I have a 5770. My question is on either system is there a need for going more than 4GB of RAM? MY laptop can do 8GB and my box can do 16+. Is there a purpose? I convert Videos, for person use, I game, and I crazy multi-task (Firefox has 50+ tabs all times, I also have a lot of apps open at once).
>4GB RAM requires a 64-bit OS, and if you do rendering including editing large images then yes 8GB+ is beneficial. Most games do not require >4GB of RAM, but there are a few that will perform better e.g. Black Ops.
If your RAM is typically running > 70% usage then yes it would be a good idea to get more RAM.
You also have to consider what applications you are using. If the application is 32 bits, it will work on a 64 bits system just fine, but it won't be able to use more than 2GB of RAM unless they use the PAE library and very few actually uses it.