Re: build questions
if you only want to upgrade for gaming @1080p, then just upgrading to an SSD will give you the best return.
Your current rig is hardly bad or outdated. Your CPU should be quite enough in games and the GTX480 will still give you quite a lot of power. Add an SSD, eventually boost your RAM if you really want to (8GB is quite enough too, but it's soooo cheap).
Always tempting to get the latest shiny, but there is hardly anything to do with it anyway.
As the universe is curved, there cannot be a straight answer...