Yeah dude, your stats look completely normal. The only reason the CPU jumps like that is because of how OS X is built. The processor is only used when you actually DO something with it. It doesn't just run when it's not needed. Really, I don't think you need 4GB of RAM per say, but it really doesn't hurt. In fact, it made a big difference with my MB. So yeah haha, your stuff is completely normal 🙂