I am also at a loss. I have built the exact machine per the above config. When I start the El Capitan install process, I get the Clover boot loader screen and it starts to install but it always stops halfway through and quits. I have removed the wifi card as someone suggested that but nothing changed. I have tried Sierra but I get a circle with slash when I begin the install process. I have a machine that works but I am unable to load the software. Any suggestions would be of great help...I have done this several times before with other machines and never had this problem. Thanks!