askschwa :
Thanks, for the responses. It would make sense to change the resolution of the iMac to match the monitors, but I was wondering if the different sizes of monitors would match up properly in game. I am stuck in the Apple Rumor mind games currently, and will wait (indefinitely) until the "New" 2012 iMacs are announced. --- Thought I could pick up a 2011 27" iMac refurbished from Apple for a pretty good price, so I was wondering if anyone had tried this type of set up before.
I honestly would purchase a PC for gaming, then put multiple GPUs into the tower to achieve the maximum amount of monitors possible, but i can agree it would be a pretty sweet set-up. Matching the 27in iMac's display to 2x 22in displays might look blown out compared to the 22in; i personally think you should look into monitors that are the same size, or close to it with the iMac, much like in the Engadget video.
In regards to waiting for the new iMac, that's going to have the new retina display probably, and i had read that not many apps, and especially games, can handle those high resolutions. If you want to do a 3 display config with the Retina, then you'll really have to dumb down the resolution on the iMac to match the external monitors, and it might really look off.
Now it might be funny if you placed your iMac really far back on the desk, so that, at a distance, it would look as if it was the same size as the 22in screens, but you're going to have to have good eyes to appreciate the detail being used on that screen.
What game or games are you planning on using this setup for?