Apple's current desktops are long overdue for updates. The current iMac is almost 1.5 years old, introduced May 2011.

I don't believe they planned to have such a long lapse in releases, especially since I know they decided to switch over to NVIDIA graphics across the board a very long time ago. The typical timeline for this decision would mean they would already long ago have release their updated machines. I suspect there must have been some issues with that move, since their mini and most notebooks are also behind. Then again, they're also long overdue for a display refresh and that could be responsible as well (it's probably why we don't have a current 17" MBP).

I posted a link to a fantastic "hackintosh" site a little while back in the video encoding thread. There are many reports of what works and doesn't work from a large number of posters, along with a number of tested systems in their recommended configuration lists.

(EDIT: Here it is: http://tonymacx86.com/)

Running the OS on non-Apple hardware is most definitely something Apple doesn't want you to do. Using such systems for anything other than "personal use" might be a big no-no. Certainly not something you'd want to publicize.