Advice needed, C602/x79 installation

Hi folks,

I need a bit of a hand with getting my build off the ground.

Currently i'm attempting to install to a HP z620 (Specifications below),

Using the following parameters to boot the installation media; (-v dart=0 npci=0x3000) i can install the operating system successfully with no errors reported. however when it comes to doing the first boot with the same parameters it just reaches a certain point in the boot process and just stops. i assume at the point where the boot process hands over to the Graphics Card.

What i've tried;
using and declaring many possible framebuffers.
loading an alternative vbios from a stock card.
all versions of El Capitan and Yosemite are presenting me with the same issue.

Has anyone encountered such an issue with similar hardware, and if so did you solve it? I've been looking for weeks for a solution for this.

Thanks.

Edit: Config.plist attached and system log (enclosing entire failed boot) attached;

Seems to me according to that log that there's nothing wrong with the installation, windowserver starts up correctly yet for some reason this isn't reflected in what i see...

**** Machine Specifications ****
Tower - HP Z620
Proc - Intel Xeon E5-1620v2
Memory - 24GB DDR3-1800 ECC
GPU - XFX AMD R9-390x
Motherboard Chipset - Intel C602
SATA Chipset - Intel C602

If you want to confirm that it looks like a graphics problem, please boot verbose (space bar from the Clover menu) and post a photo of the screen where it stops.

Otherwise, this might be a good question for the Graphics forum (you've already surpassed my available Radeon experience