Hey. I'm about to purchase a new iMac, but I don't know a thing about hardware. I'm torn between buying the 21" 3.06ghz with 8gb or the 3.20ghz with 4gb. I'm trying to figure out, which one would perform faster? And, if I were to go with the 3.20ghz model, would it perform faster if I upgraded it to the 3.60ghz chip or if I upgrade it to 8gb of RAM?