you aren't going to do much better without upgrading your mobo too
both arma and rust seems to list either 4690k or a similarish i5-4000 series chip in their recommended settings, while kerbal very ambiguously states a recommendation for "i5", so you should be covered there
no idea where you're buying from, or what prices you're looking at but there's a pair of obscure broadwell processors, i5 5675c/i7 5775c, for the 1150 socket, which despite their lower clocks are slightly faster due to the smaller 14 nm process. if you can find those...
also can you game comfortably in fullhd with the 770, or do you even care about that? there's quite a bit of newer older cards moving, with decent prices in the used market ATM
