It's about time to upgrade my iMac's RAM, and I have a couple questions. - Where can you get the cheapest RAM? - Is it possible to use my existing 1GB stick and add a new 2GB stick to make 3GB? On the Apple configuration page, it only shows 1, 2, and 4. 3GB seems like a happy medium. Sorry if these are noobish questions, but I've always just used the stock RAM.