If there is not that much of a difference now, wouldn't it be better to pick i5 and see how the new one, coming in 2015, will do and change it later if needed?
An i5 and 780 would be a good combo. I think there are only a few games that take advantage of the i7's Hyperthreading. If you were doing other things like Rendering and Video Editing then the i7 would be more beneficial.