What would more ram do for this computer?

the only way you can truly have too much RAM is if you have so much that seek times are slowed down as a result. if the OS won't support it (most 32bit OSs only support 4GB for example) then it simply won't use the rest. If you have a 64bit OS then I would go with 6GB or 8GB (I'm fuzzy on the DDR3 rules but I know my ASUS rampage MB requires RAM in sets of 3 or else it runs at DDR2 speed and not DDR3... however I see a lot of MBs that use DDR3 with only 4 RAM sockets which makes it hard to add RAM in sets of 3). for gaming 4GB will usually do just fine and higher end games may make use of more RAM but if you are just playing something like WoW then 4GB is overkill.