The FTW models from EVGA are just a bit better than the reference model and worth getting , however if your getting the FTW model of the 660Ti then that would be ok too. I'm guessing it would depend on what your useing the Pc for and if it's gaming the what settings , what games and what resolution are you looking at?
It ends up a more complicated decision then which video card should you get.
While the 600T case is a realy nice case it can't add to the performance or add to the fps of a game , it's just nice to look at and might have more features so your choice is really about going with a 660Ti or a 670 FTW.
I would go with the Evga 670 FTW.