iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Amazon.com: 2GB Graphics Video Card Replacement for Apple iMac Mid-2011 27 Inch A1312 Core i7 3.4 MD063LL/A MD063 Desktop PC Computer, ATI Radeon HD 6970 GDDR5 2 GB, New GPU Upgrade Repair
4GB/8GB PC3-10600 DDR3 1333MHz iMac Mac Memory / RAM Upgrade for A1278 A1286 A1297 MBP Pro A1311 A1312 27-inch A1347 Mini | Lazada
Amazon.com: 2GB Graphics Video Card Replacement for Apple iMac Mid-2011 27 Inch A1312 Core i7 3.4 MD063LL/A MD063 Desktop PC Computer, ATI Radeon HD 6970 GDDR5 2 GB, New GPU Upgrade Repair
8GB [2x4GB] DDR3 RAM Memory for Apple iMac model# iMac12,1 iMac12,2 A1311 A1312 | eBay