So to close the loop on this, I have settled on using 3 separate rigs for this.
1. i7 4790, 4 core 8 threads total, cracking rate of 13 H/s, cost of $330
2. Xeon 1220 V3, 4 core 4 threads total, cracking rate of 8 H/s, cost of $180
3. Xeon 2667 V3, 8 core 16 threads, cracking rate of 21 H/s, cost of $560.
I tested JtR and hashcat on all of them. JtR does better on i7 4790 and on the Xeon 1220 under Linux. The difference
was between 10 - 20 percent.
Hashcat on Windows did better than JtR on the Xeon 2667. The difference was much bigger, at about 25%.
Altogether, I have 2 instances of JtR on Linux and 1 instance of Hashcat on Windows doing about 42 H/s.
The other rigs( FX8320 and I5 750) were not cost effective to use.
1. i7 4790, 4 core 8 threads total, cracking rate of 13 H/s, cost of $330
2. Xeon 1220 V3, 4 core 4 threads total, cracking rate of 8 H/s, cost of $180
3. Xeon 2667 V3, 8 core 16 threads, cracking rate of 21 H/s, cost of $560.
I tested JtR and hashcat on all of them. JtR does better on i7 4790 and on the Xeon 1220 under Linux. The difference
was between 10 - 20 percent.
Hashcat on Windows did better than JtR on the Xeon 2667. The difference was much bigger, at about 25%.
Altogether, I have 2 instances of JtR on Linux and 1 instance of Hashcat on Windows doing about 42 H/s.
The other rigs( FX8320 and I5 750) were not cost effective to use.