check the thread about hooking up the xbox 360. Its the same thing we are trying to accomplish. basically, you need something that upscales and converts. Currently the only hardware solutions are produced by the company atlona. you need the dp200 and the hd560. cost is close to 400 dollars just for this setup.
Ive already got them ordered and will be ordering my imac shortly... i will post results when i get everything together.