My biggest recommendation would be to reevaluate your GPU choice. You want a blower style card like the 1080 FE's.
The cards you have listed will exhaust their hot air INTO the case and onto the video card below it. This will cause severe heat issues in a multiple GPU scenario.
Also consider your ram. In a previous post, the hashcat experts here recommended a bare minimum of 1gb of system ram per 1gb of total vram. If you go up to 6 1080tis, that would be 66gb of vram. Based on this, I would just jump for 128gb of ram. Wordlists are also preloaded into ram so more helps.
The cards you have listed will exhaust their hot air INTO the case and onto the video card below it. This will cause severe heat issues in a multiple GPU scenario.
Also consider your ram. In a previous post, the hashcat experts here recommended a bare minimum of 1gb of system ram per 1gb of total vram. If you go up to 6 1080tis, that would be 66gb of vram. Based on this, I would just jump for 128gb of ram. Wordlists are also preloaded into ram so more helps.