the i5-2500k is a very friendly OC chip. I just set my voltage to auto and then set multiplier to 45. voltage in prime95 is about 1.3, in games a little lower, sometimes voltage spikes to 1.35. don't really care, it doesn't seem to hurt anything.
it's also a very good chip that is still very viable today. I have a gtx 1070 (evga sc) and I basically play ultra in everything, all maxed out, with anywhere between 75fps (witcher 3) to 90 fps (bf1) to 144 (doom). yeah, I think i'm ok with not upgrading for a while.