I've got the late 2009 iMac with the following specs: Processor: 3.06 GHz Intel Core 2 Duo Memory: 4 GB 1067 MHz DDR3 Graphics: ATI Radeon HD 4670 256 MB Hard Drive: NVidia MCP79 AHCI 1 TB (this is a replacement by Apple about 1.5 years ago when the original was recalled) Running: Mac OS X Lion 10.7.5 It's running slow, seeing the beach ball fairly often. I've got about 500 GB free, most stuff is on an external, but large music library (over 200 GB) is on the computer itself. I'm not in a position to buy a new machine, hoping for advice on memory upgrade specifically. Although other suggestions would be great. It's got the original 4 GB (2x2 GB). Crucial has 2x4 GB avail for about 90$, which would bring memory up to 12 GB (would this be enough for a performance increase?). Or I could pony up and get 4x4 GB for a total of 16 GB (is this necessary?) and scrap the 2x2 GB sticks. I've hesitated upgrading to Mavericks because I don't want a further slowdown. Typical uses are iTunes, Safari, mail, iPhoto, Firefox, word, excel, adobe reader, VLC, Vuze once in a while, calendar, etc. It's really just a personal machine, but definitely not kicking like it once did.