since most games are still not using all the extra threads, going from 6 to 8 cores that are not any faster does little overall for the pc.
the jump from an r9-270 (roughly the same as a 750ti) to a 1060 (roughly a gtx 980 in power) would be a much better jump and net the best results for games. i'd not bother upgrading the 6300 until you can afford to move to newer gen cpu's which of course means a new cpu/mobo and ddr4 ram no matter if you go amd or intel newest gens.