FWIW,
I have the 2011 i7 27in and 2010 i5 2.8 27in - given the options and costs, for now the i7 2.93 represents great value - regardless of whats said, iMacs really are not gaming machines, obviously they can be used for gaming, but an Xbox or PS3 seems a better bet for this after reading these boards.
TB is new technology and not many add ons as of today, costs will also be high - nothing wrong with FW800 and this will be supported for at least another three years.
Buy the i7, get AppleCare and you have a good machine for 3 years - add more ram, forget about SSD and run additional storage via FW and TM via USB.
Hope this helps, but refurbished i7 represents excellent value in a machine that cost nearly US$2,500 only two months ago.