Hi, I'm building myself an eGPU for my MBPr 2015 13". I've purchased:
Akitio Thunder2
GTX 970 ITX (https://www.amazon.co.uk/gp/product/B00P7337YG/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1)
For the power supply:
Dell DW-2 (http://www.ebay.co.uk/itm/231191384558?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT)
1 Barrel plug (male) (https://www.amazon.co.uk/gp/product/B00JRGQLWO/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1)
2x PCIE splitter female to male 8 -> 2x 8 (https://www.amazon.co.uk/gp/product/B003T7071I/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1)
2x PCIE splitter female to male 6 -> 2x 6 (https://www.amazon.co.uk/gp/product/B004NNTVT6/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1)
To confirm what I think I'm going to do is...
Take Dell adapter.
Plug in my 8 PIN splitter (1 row across so the left column of pins on the dell are exposed. then put a paper clip from the sense into a 12v point
This gives me 2 additional 8 pin plugs.
Take 1 of these and solder them into a barrel plug. 12v & Grnd.
Take the other and plug it into a 8 to 2 8 splitters.
Plug 1 of these into my 970.