In my tests, the i5 and i7 didn't offer much more performance over the 8320 FX. In many the i5 fell far behind and in most the i7 only offered 5 more fps over the 8320 FX. That was between the i5 4690k, i7 4770k, and of course the 8320. Most AAA titles coming out now can use up to 8 threads (Theif, Watchdogs, Crysis 3(a bit dated now), Battlefield 4, and The Evil Within are just a few examples).
Other than that, Montblanchill is correct. At these resolutions the 8320 is going to be your best bet, due to the lower cost of motherboard and CPU combo's. Matter of fact, my recommendation would be the 6300FX series of 6 core CPU's from AMD. Even then if may be overkill, so you could still go with and i3 CPU.
I would like to note I am not a particular fan of either company. I definitely prefer Intel over AMD but that's due to the fact I do 3-D modeling and Unity Engine editing for indie games. Meaning I get the most out of hyper-threading. I also game at 1080p resolutions and soon will be upgrading to a 1440p display. For strictly gaming, unless your an enthusiast or some kind of Otaku, I generally build with AMD due to lower cost for performance. Granted they run hotter, you can make up for that with a decent cooler like the Hyper 212 Evo.