As the others have stated there really isn't much advantage to go with an Intel® Core™ i7 over an Intel Core i5 processor for a gaming system. Unless you are really doing a bunch of work in the background which it doesnt sound like you are then the Intel Core i5 is the way to go.
Not only is the i5 a better value, it's often a better performer in an absolute sense. The only time the i7 pulls ahead is when both CPUs are already pushing well over 100 FPS, i.e. in applications that are optimized for eight incongruent threads.