if you don't want to spend any money for an upgrade you might not need (but if you are seriously considering 5 boxing 8G ram is just about a must, even upgrading from 4 to 8 with your current specs will improve your performance in cities and high pop areas) i would suggest you just try 5 boxing with a trial account and take all 5 of your characters into cities and places where you already may have some lag issues and if your system is playable by your standards then you could probably hold off upgrading for a little while. but if you are going to 5 box just about everybody here would recommend you increase your RAM from 4G to 8G.

hope this helps ^_^

~YYF