There is really nothing you can buy or use on that platform that is going to offer you any meaningful increase in performance. It is simply too far out of relevance to be useful anymore. Obviously, if your board supports it and you slap a used i7-860 in there you gain four simultaneous hyperthreads, which might help some small amount on games that are well optimized for multithreaded performance, but honestly anything invested into that platform, unless you can find a CPU for less than 20 bucks, is a waste of money that would be far better spent towards something that would help get you onto a newer platform.