Today picked up a $20 2011 iMac 27” with working gpu too! : r/mac
Install memory in an iMac - Apple Support
iMac Mid 2011 (21.5 – inch and 27 – inch) RAM Upgrade Dallas – Apple Mac Computer Repair Dallas , Laptop ,Desktop ,iMac ,MacBook iPhone iPad Data Recovery ,Virus
NEMIX RAM 32GB (4x8GB Upgrade) DDR3-1333 PC3-10600 204-Pin SODIMM Memory for Apple MacBook Pro Early/Late 2011, iMac Mid 2010 27 inch 4-Core, iMac Mid 2011 21.5/27”, Mac Mini Mid 2011 at Amazon.com
A-Tech 32GB (4x8GB) RAM for Apple iMac (Mid 2010 27 inch 4-Core, Mid 2011 21.5/27 inch) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Kit at Amazon.com
Installazione RAM iMac Intel 27" EMC 2309 ed EMC 2374 - Guida di riparazione iFixit
Amazon.com: Timetec 8GB KIT(2x4GB) Compatible for Apple DDR3 1333MHz PC3-10600 for Mac Book Pro (Early/Late 2011 13/15/17 inch), iMac (Mid 2010, Mid/Late 2011 21.5/27 inch), Mac Mini(Mid 2011) RAM Upgrade : Electronics
install - Installing and Upgrading Ram on a mid 2011 iMac (different size RAM) - Ask Different
Apple iMac 2011 (Mid) 27-inch 2K (iMac 12,2) SSD ,Ram & OSX Upgrades - ZD Laptop Service Centre