I have a mid-2011 27" iMac. Specs are: 2.7Ghz i5 20GB RAM (probably sell with 16 for an even number) 1TB Hard Drive Apple has this model refurb for $1439, but I've seen 1 or 2 on eBay go for over $1600. Might just be an isolated incident where people failed to price compare. So realistically what is it worth? I'm asking because I'm thinking of getting a 13" Air and a Cinema Display to replace my desktop. Thanks.