I would just drop in something like a 965BE quad, unlocked multiplier, easy to bump up.
You may want to add another 4 gig of memory if you feel you are running low, but overclocking/faster memory won't net you any noticeable gains. So I would just get another pair of what you have.
But honestly, don't expect miracles here. Gaming and internet browsing, with a couple of open Windows is not what we consider heavy multi tasking. If you have the money for this upgrade and don't mind spending it for some marginal performance gains, I would do it. If you are tight on budget though, I would just hang on for a while longer. The money would be better spent on a new platform.
So just 2 more sticks of what i already have? I was under impression that 2Gb 1600MHz 9CL is a bit weak, there is much better memory out there now at this point.
Also, what do you think about 1100T instead of 965 BE?
And one last question, are SSD worth the money at this time or should i wait a bit longer for the price to drop? From my understanding SSD will just launch my applications faster... and this is pretty much the only benefit from it.