Want to make 7 GPU rig, need feedback

Hi all,
I am planning to make a 7 GPU mining with the following parts in India:

CPU -> intel Pentium G4400
MotherBoard -> MSI Z170A Gaming Pro Carbon Motherboard LGA 1151
RAM - Kingston HyperX FURY Black 4GB 2133MHz DDR4 CL14 DIMM
120 GB SSD
PSU - 2 ANTEC EDGE 750 750W

and I am thinking to go for either 470 or 570 which are available at the same price.

I have access to free electricity to next few years so power consumption is not an issue.

I can also get 480 or 580 which are like 40-70$ costlier than the basic 470/570s, but would like to know some views on what card to choose.

Also while suggesting kindly mention the brand/model number and expected hashing rate.

Also is there any benefit for choosing 8 GB version over 4 GB version.

Any help/advice on whether I should build it today, what card to choose, what PSU to choose etc would be really awesome.