Need help building hobby rig.

[Flomac]

Most of the case/MB-combination depends on the cooling of the GPUs. If you can use GPUs with radial coolers you can stack them close together. That is not possible with GPUs runnig axial coolers, cause they just heat up each other, even in an open case like the one you've posted.

One SSD with >250GB should be fine for usual hashcracking.

The RAM equal your GPU RAM in size (or a bit less).