I'm thinking about selling my mid 2011 air to upgrade. I try to do this so I can at least recoup some funds w/o falling to far behind in upgrades. I have a 13" mid 2011, w/ 1.7 ghz, 4 ram & 256 flash. Great condition, no scratches, dings or cosmetic wear. How much do you think I can get. Paid $1,500ish, then. I also have a new booq viper sleeve (sand) that I don't care for. Thanks.