Some of my results that I would like to share with the community:

2x Xeon 2667 V2: 1200-1300 H/s. Power consumption of each CPU: 100W
2x Xeon 2690 V1: 950 H/s Power consumption of each CPU: 100W

So yes, you can make good returns with CPUs you already own. I just happened to have these workstations: not sure I would have recommended anyone to buy these just for mining!

Oh: added benefit. No need for heating at home