Trust me, there's no way he could get a reasonably priced upgrade to that CPU. High end Socket 775 quads are rarely available and expensive. It wouldn't even be worth it, he just needs to overclock it.
To that guy: also don't invest in 8GB if all your slots are filled, unless you get a seriously good deal. DDR2 isn't going to be a great purchase if you have to replace all your RAM.