I am close to purchasing an iMac after being a PC user for many years. My original plan was to buy the 24 inch 2.8 ghz model. After looking at it again, I am thinking of dropping down to the 20 inch 2.4 ghz model . In both cases I will be upgrading to 4 gb of memory. I found it online for $125. Will I notice the processor speed (2.4 vs 2.8) difference and will it cause any issues? The one thing that is the same is the video card (ATI Radeon HD 2600 PRO with 256MB memory). I suspect the video performance would be better on the smaller screen but I am not really sure. I didn't notice any upgrade options for the video cards. Is this true? I am also thinking of buying a refurbished model (from apple) instead of a new model. Other than typical web browsing and email, my main use for it will be playing World of Warcraft. Any thoughts? Thanks.