first of all, if you actually want to learn about all this you should check out the guide that's in my signature. it's got pages - literally, pages - of computerspeak turned into plain english. which is why i wrote it.
download a program called cpu-z, run it (no install, just run the .exe), and tell us what's under the motherboard pane. a screenshot would be glorious.
depending on what you've got, i'll be able to give you definitive answers on what to get based on what kind of cash you've got. this is, after all, what i do with my computer business, after all =)