Starting at $1199, the 21.5-inch has a 2.5GHz Intel quad-core Core i5 with 6MB on-chip shared L3 cache, 4GB RAM, a small 500GB HDD and a 512MB GDDR5 AMD Radeon HD6750M video card.
The more expensive model starts at $1499 and has a 2.7GHz i5, a 1TB HDD and an AMD Radeon HD 6770M. It can also be upgraded (very expensively) to a 2.8Ghz i7 processor, a 2TB HDD and a 256GB SSD as a secondary (or primary) drive.
Moving up to the 27-inch models, starting at $1699 you can get a configuration with a 2.7GHz i5, a 1TB HDD and an AMD Radeon HD 6770M.
The most expensive base model starts at $1999, bringing a 3.1GHz i5 and a 1GB AMD Radeon HD6970M. That model can be modified to add a 256GB SSD, a monster 3.4Ghz i7 and a 2GB version of the video card.
Each computer has a mini display port, a FireWire 800 port, 4 USB 2.0 ports an SDXC card slot, gigabit Ethernet, Wi-Fi and Bluetooth and an Apple wireless keyboard and Magic Mouse. Additionally, each has 2 new Thunderbolt ports and built-in HD webcams for FaceTime.