Hi, I'm new to apple iMac. I want to change from my PC world to a mac, and love the way the iMac looks. I would like to buy a used one. Should I get a 20" or 24"? Is the graphics that much better on a 24" How important is the processor speed vs ram? wireless or wired keyboard? I see some hard drive failures in the forums is this the exception? I would like to spend less than $1000 Most of what I do is surfing the internet and running Microsoft Office apps. Thanks for your help How reliable have these all-in-one computers been?