i5-2500K (4 cores) @ 4.5 GHz - 33.6K hps

i5-4690K (4 cores) @ 4.6 GHz - 38.5K hps

Xeon E3-1275 V2 (4 cores/8 threads) @ 3.7 GHz - 32.5K hps

Pentium G3258 (2 cores) @ 3.2 GHz - 13.5K hps

Phenom II X4 (4 cores) @ 3.2GHz - 17.1K hps

Why don't you mine with 8 cores? You can mine with all cores and still have CPU power available when needed if you lower the process priority of steemd with nice/renice.