ExperCom offers the Apple iMac Intel Core i7 3.4GHz 27" Desktop
upgraded with 16GB RAM
plus around $29
for shipping. That's tied with our January mention and it's $471 less than what Apple charges for the same configuration. (We listed this model in December bundled with AppleCare for $87 more. Features include an Intel Core i7 i7-2600 3.4GHz Sandy Bridge quad-core processor, 27" 2560x1440 LED-backlit widescreen glass LCD, 16GB RAM, 1TB 7200 rpm hard drive, SuperDrive, Radeon HD 6970M 1GB graphics, AirPort Extreme (802.11n), two Thunderbolt ports, FaceTime HD camera, Bluetooth 2.1+EDR, Gigabit Ethernet, and more.
Note that ExperCom does not specify which OS this iMac contains.