some hardware questions for building a new rig

Have been reading several threads, and my understanding is that the GTX 1080Ti is the card to buy.
Thinking about buying 2. Will mainly use them for cracking NTLM/netNTLM/WPA2.

• Any particular GTX 1080Ti brand that is recommended or brands that I should avoid ?
  
• OS will be Linux,  should I go for Ubuntu 14.04 or 16.04 LTS or another distro?
  
• How important is storage? Is an SSD a must have?
  
• Is 32 GB RAM enough? Or can I expect higher speeds with more?
  

Thanks