Testo :
My resolution is 1280 x 1024 at the moment with this old screen. I am going to buy a new screen with a bigger resolution. And the games I intend to play the most are Battlefield 1 and Dishonored 2. What effects would the upgrade bring in this case?
I do not know. I only know about BF1 from the experiences I read about.
And... nothing about dishonored.
I suggest first, you buy your new monitor and do some testing.
Buy your new games and see how you do.
Then, decide if you need stronger cpu or gpu.
I would normally say that a upgrade to GTX1060 would be appropriate for 1080P
A graphics upgrade is easy. That assumes you have sufficient psu power. GTX1070 may need 500w.
Then, reading I have done suggests BF1 may be cpu limiting.
But, if you will be playing multiplayer, then a quad core can be very good.
Unfortunately, updating to skylake will be more of a problem, needing a new motherboard and ram also.
Anything less than a I5-6600K is not likely to be a big boost.