• for $2199, you can get the top of the line iMac, with a core 2 duo at 3GHz (that's 2 cores)
• for $2799, you can have the basic Mac Pro, with 8 cores at 3.2GHz.

IMO, if you can afford it, your way better off to buy the lowest end mac pro octocore (8 processors) than the top of the line iMac 2 cores. The 8 core machine will render a LOT faster and has the ability to upgrade to a faster video card too.