After browsing the threads from search I have a question. Most people who do this upgrade (to two CPUs) upgrade the speed of the processors at the same time so they do end up needing to buy matched pairs. But if I am just wanting to add the second processor to what I have, am I still stuck with needing to buy a matched set or is it possible to stick the exact model CPU in with heatsink and power up? If so, what is the exact model I should be looking for? Sorry if this is such a basic question but I am always confused with the seemingly countless different steppings and listings I see on auction/used sites.