Need spec assistance on a build

[KT819GM]

Ive just told for your goal - so yes, you need only 4 pciex1 4 risers, 1 cheap motherboard with sempron like cpu, 2 gb ram, and 1 8 GB usb key for os install. All that will be price dependent - GPU's and PSU's. On psu you can save money by buying older one from server racks 1,5 or 2KW units at ±40 usd, but then you also will need some tech knowledge to attach it to your cards without burning them.