I bought my first iMac in 2014. It is a 21.5" 2.7GHz quad-core Intel Core i5 Non-Retina. It has 8gb RAM and a 1TB Flash Hard Drive. My machine is primarily web surfing, email and creating a few documents here and there. As of this writing its still sailing along nicely. I'm fairly deep into the Apple ecosystem and am getting the itch to upgrade. I've been offered $400.00 for the machine. Is it time or hold out? I'd like to sell my old system while its still worth something.