1440p is not medium resolution and certainly requires a good amount of raw power if you want to push that resolution above 100fps with all the eye candy on and if you reply with a "1080ti is a 4k card" i'm going to reach through the infinite spacetime and slap you silly with a white glove
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. The OP didn't specify what i5 or i7 he talked about but lets for arguments sake say its only the 8600k and 8700k then the point i wanted across still stands.
If i had bought the 4690k(or 4670k) instead of my i7 i would be having not so great a result right now which leads to my point all along. I5 may be just fine right when they come out, the 8600k is certainly faster than my aging 4790k, but it wont be long before you wish you had that hyperthreading to help you out simply because core count requirements are going up. Its not a fast change but if you plan to keep your system as it is for a long time it certainly makes sense to spend that little bit extra and then be able to skip another 1-2 generations(going by the last few years). We already right now have games(yes multiple) that will max out a 6 core 6 thread cpu, sure would be nice if budget allows to have those extra 6 threads in such a situation.