4 card cracking Rigg

Hello Fellow Crackers

I am planning on building a new hashcat rig with a budget of 3000 euros. 

I made the following graph based on the actual prices:

                ntlm MH/s    Price     price/ntlm         amount        total ntlm      Total gpu cost
1080ti       52715.6       800       0.015175773    2                  105431.2      1600
1080         41354.8       580       0.014024974    4                  165419.2      2320
1070ti       39107.7       495       0.012657354    4                  156430.8      1980
1070         29890.8       470       0.015723902    4                  119563.2      1880

I currently have the following rig:

• i7 3770
  
• 32gb 1333mhz ram
  
• P8Z77-M PRO (mATX)
  
• 2x gtx 760 fe
  
• 1600 watt psu
  

So I am thinking of buying new cpu, mobo and ram:
i5 8400                                          183,-
Corsair vengeance 32GB 1600mhz    311,-
Asus ROG Maximus X Apex              311,-
4x 1070ti                                       1980,-

for a total of 2781,-

I still have a couple of questions:

1. Does the CPU matter for hashcat?
   
2. Does the amount of ram matter for hashcat?
   
3. Does the speed of the ram matter for hashcat?
   

I would like to hear your guys opinion and feedback.