What do you think of this build?

I'm looking to build 3 of these...ideally I'd like to have 7 rx570s / rig. The 470s are tough to find in a large quantity so I'm going with 570s.

Here's my current build:
https://ca.pcpartpicker.com/list/QCqLxY

My question is:
1) Is it possible to power 7 GPU with one psu? The one I have has 6 vga ports, not sure where to plug in the 7th

2) How good are these adapters?

http://www.ebay.com/itm/PCI-e-Express-1X-to-3-Port-1X-Switch-Multiplier-HUB-Riser-Card-USB-Cable-1PC-/141865200790?hash=item2107d32c96:g:zTwAAOSwa-dWhMvm

Seems like a nice addition to power 6+ GPUs