Small world, like you , I picked up 2 x E5-4665 v3 for $180 total. There is no warranty for the CPU, sold as-is.
In last couple of years, only had 2 cpu that were actually defective.
E5-4665 v3 for mining, the spec looks ok, the price are cheap.
Dual E5-4665 v3 CPU , 1.1K H/s @ 192watt = 5.7 H/s per watt
Dual E5-2650 v3 CPU , 0.9K H/s @155watt = 5.8 H/s per watt
The E5-4665 v3 have L3 30MB ( good ) , base clock is 2.9Ghz ( good ), 6 cores - 12Threads ( not so good ).
Because the smaller amount of 6 physical cores, it is not using the full L3 cache.
I am using Ubuntu 16.0.4 with xmr-stak-cpu, may be you could try to see if there is hashrate increase.