About to buy hardware

Hello

I am new to this forum and the hashcat software.
I wold love to make a low budget rig that i can upgrade when i have some more money.

What GPU shold i take?
I was thinking about the GeForce 1080 or GeForce 1080 ti (only 1 yet)

What motherboard shold i take?
Maybe something big? so i can later on buy a few more GPUs

What CPU shold i take?
Shold a i5 Exeon get the job done? and shold my motherboard have 1 or 2 cpu sockets?

The Powah!
How about this one? so far i am only planning on using 1 GPU, but it wold be handy to have a good one so it doesnt become useless when i get another GPU.

RAM?
How much ram shold i take? and how many slots shold i use / save for later?

Storage HDD/SSD?
I don't think i need a SSD for this, a hughe but slow HDD shold get the job done?

Wich OS shold i use?
It wold be nice to use the rig as a rendering farm / cracking rig or even Miner.
The goal is NOT to make it a miner, but its always fun to play around and test out new things.
Anyways, remotely connecting to the rig is also something nice i like.

Hopefully u can help me, i just can't wait to get started!