at 3.40 ghz his i5 is really good, The difference with a i7 is so small that he wont event notice it. If your computer is only for gaming, getting a I7 in your case its useless. Just with a new GPU you will see the difference. And About the SSD, Since I bought mine I cleary see a difference in game. Loading and everything. I have a old 2600k i7 OC at 3.8 ghz . I had a gtx 560 , 8go of ram and an HDD. I upgraded For a gtx 1060, 16 go ram DDR3. and Samsung SSD 500go. The difference is Huge. I never drop below 60 fps, I load way faster and im playing with graphic at HIGH , a Distance of 8000+. Since arma updated to 64bit, I never got a frame drop or any type of lag.
Edit: Since he have a 3.20 ghz( Witch I tought I saw 3.4) Getting a more powerful CPU will make a difference. But you can get a I5 at 3.40+ Of the year for half the price of the I7. What im trying to say is that you don't need to pay for an I7 If you intention are only for gaming. A i5 is perflectly fine