Build recommendation ~2.500€

Hello guys,

I'm looking for a password-cracking build for about 2500€.
The machine should act as a Cracklord-resource (if you don't know what cracklord is: http://jmmcatee.github.io/cracklord/)... so it has to run Linux (I will probably Debian/Ubuntu)


Since I was looking for some nice builds, there came up some questions:
What are the best cards for this build? (e.g. 2x 980 ti || 1x titan x)
Is much RAM and a strong CPU important?


Thank you