More or less new to mining, setting up a small machine starting with 1 GPU and possibly expanding to 3. I work at an electronics retailer and got some good deals on open box components, here's what I have so far:
Asus TUF Z270 Mark 2
Pentium G4400
Patriot 4GB DDR4-2133
750W 80+ Gold PSU
128GB NVME SSD

"Case" will be a milk crate.

I've narrowed down GPU to an MSI Armor RX 580 8GB due to good cost vs return
https://www.amazon.com/MSI-RX-580-ARMOR-8G/dp/B06XZQMMHJ/ref=sr_1_1?s=electronics&ie=UTF8&qid=1528293419&sr=1-1&keywords=msi+rx+580+8gb
I also see they have an MK 2 version which runs at a higher clock speed
https://www.amazon.com/MSI-RX-580-ARMOR-MK2/dp/B079NX4GCF/ref=sr_1_1?s=electronics&ie=UTF8&qid=1528288552&sr=1-1&keywords=msi+armor+mk2

So, any feedback on the following would be appreciated.
1) Which of the above 2 cards, or something else in the $300 range?
2) Currently I'll be using NiceHash, which is nice and easy, others I should look at?
3) General thoughts/tips on my setup?

Thanks!