What about using the new Ryzen processors?
They do very well at CPU mining, easily the best CPU miners aside from server grade Xeons etc. With a Ryzen 1700/1700X/1800X you can expect to get 600+ Mh/s with Monero and it does well in many other coins too.
600+ Mh/s! The Monero world mining hash rate is 233 MH/s.