try one other thing plug one of the cards into the motherboard direct don't use any raiser cards plug into the PCIE 16 X slot on the motherboard that MB has one the rest are X1 slots if that works then check how you are powering stuff etc and make sure you RC are good ones other wise no idea other then reset the bios at the mother boards jumper then try or re install windows sense you can see the mother boards post screen use a USB boot drive or CD .. that should let you re install windows ..or do a windows PE install with a boot able usb Drive that seems to install faster and better. then doing it the Setup.exe way ..
wish i could help more or see it, i can probable get it working if i had it in front of me ...
Cya and GL
PS : last thought make sure the card you are using with the monitor is plugged in to the x16 slot with the rasiser cards and not any of the x1 slots or it may let it boot but won't show a picture after the post boot screen of the MB ...but boot into windows .. or
If you have an Intel board and have network connectivity issues or are unable to successfully boot with multiple GPUs, follow the below instructions:
If you have many GPUs, make sure that no GPU is plugged in directly to any 16x slot. Risers must be used for all GPUs.
Unplug all GPUs except for gpu0 (ignore all 1x slots, gpu0 is always the 16x PCI-E slot physically closest to your motherboard's CPU socket).
If your motherboard has molex or PCI-E onboard power jacks, make sure to plug the correct cable into them.
Upon boot, go into the motherboard bios and set the following options (set as many of these options as you can find):
set BOOT ON POWER to ENABLE (enables rig to boot by flipping PSU Power Switch).
set VTd INTEL VIRTUALIZATION to DISABLE.
set ONBOARD AUDIO/SOUND (AZALIA) to DISABLE.
set IEEE1394 to DISABLE.
set PCI-E SUBSYSTEM/LANES to x8/x4/x4
set ONBOARD GRAPHICS to DISABLE.
Save changes and reboot.
that comes form here
http://ethosdistro.com/kb/#booting-intel-boards 
