Complete overkill in my opinion, but I like spending money, so I'll allow it.

Mine runs on an i3 and generally gets around 10-30% CPU usage, never anything even close to taxing.

Where did you source the ISO's from.

I realize you've tried and used multiple ones. I'm just curious, because I've ran both 7 and 8 clusters and I have never seen this issue except on poorly sourced or broken images.