Yes, both are reference designs. And you can also use two of them in one machine.
That said the rest is less important. Get a SSD and you're fine. 16GB RAM and you're fine.
CPU is needed only for the CPU version of hashcat and stuff like sorting or zipping, so a nice i3 with HyperThreading performs ok and sufficient under hashcat. The bigger Quadcores without HT are not that big step forward compared to their price. The next push comes from the Quadcores with HT, like a 4790K, but the price jump to the i3 is rather big. Tip: a Xeon CPU gets you Quadcore and HT and only lacks the overclocking feature. If you don't want to overclock anyway, it's your choice (E3-1230/1231/1240/1241, all v3 because that's the newest Core with AVX2). All these are socket 1150 of course. If you really want to do lots of CPU hashcat a 6-core i7-5820X might even be better for you. AMDs 8320/8350/8370 is also a good and cheap alternative, although the motherboards are a bit outdated.
A good motherboard with chipset Z-series will be prepared for two graphic cards. Wouldn't be bad if your case has some coolers to keep everything silent. If you don't have a case, take a look at the Cooltek W2, it's very nice.
That's it in a nutshell
And most mportant, don't save money on the PSU. 1000W are fine if you use two GTX980. If you plan to enhance someday to a third or even fourth, get a 1200W or 1500 model.
That said the rest is less important. Get a SSD and you're fine. 16GB RAM and you're fine.
CPU is needed only for the CPU version of hashcat and stuff like sorting or zipping, so a nice i3 with HyperThreading performs ok and sufficient under hashcat. The bigger Quadcores without HT are not that big step forward compared to their price. The next push comes from the Quadcores with HT, like a 4790K, but the price jump to the i3 is rather big. Tip: a Xeon CPU gets you Quadcore and HT and only lacks the overclocking feature. If you don't want to overclock anyway, it's your choice (E3-1230/1231/1240/1241, all v3 because that's the newest Core with AVX2). All these are socket 1150 of course. If you really want to do lots of CPU hashcat a 6-core i7-5820X might even be better for you. AMDs 8320/8350/8370 is also a good and cheap alternative, although the motherboards are a bit outdated.
A good motherboard with chipset Z-series will be prepared for two graphic cards. Wouldn't be bad if your case has some coolers to keep everything silent. If you don't have a case, take a look at the Cooltek W2, it's very nice.
That's it in a nutshell
And most mportant, don't save money on the PSU. 1000W are fine if you use two GTX980. If you plan to enhance someday to a third or even fourth, get a 1200W or 1500 model.