dont buy the i7, if you want i7-4790 buy xeon e3-1231 v3, its the same processor without integrated graphics (which you dont need cuz you have a graphics card) but cheaper. Got it myself.
I5 7600 4sure
Don't even compare 4.gen vs 7.gen
If you want to play and stream, go for the i7. hyperthreading will give you good performance.
If you just want to play the game, buy the cheaper i5. U'll lose a couple of FPS that you would not notice anyway and save the cash for an SSD or GPU upgrade.
You have to consider the motherboard as well. 4th gen needs 1150 socket, 7th gen needs 1151 socket. The IPC gains are not huge from 4th gen to 6th gen.
i5 or i7 with "k" overclock to 4500-4600Mhz and easy very nice fps on any map 5on5 (stable 300 without downgrade)