macguru9999
A suggestion.
Buy an EVGa PowerLink ; it balances all power fed to it and then on to the GPU.
Although originally designed for Nvidia cards it works just was well with AMD cards as well if set up correctly.
My MSI Armor RX 580 8gb is not EFI flashed and I only have two 1080 monitors but I power my RX 580 thusly ..
1. TWO X Mini 6 pin to ONE 8pin - this goes to the PowerLink's 8 pin INPUT female socket
plus . .
2. TWO x SATA to a MALE SINGLE 6 pin - this goes to the right side of the PowerLink's other
female 8 pin socket.
The combined power from "1. " & "2" go from th e PowerLink to the R9 580's 8 pin female socket
plus . . .
3. The PCIe slot power.
If I'm not wrong - correct me if I am. . . . the total is over 300w.
Note : Because the R9 580's 8 pin socket's cable lock tab now faces DOWNWARDS I had to connect the PowerLink remotely = it sits on top of the PCIe area's INTAKE fan - held firmly in place with an eraser
😀.
I just ran Heaven at HIGH + Anti-aliasing X2 and was pleasantly surprised with the benchmark, it is the highest I have achieved since adding the extra two SATA to 6 Pin power.
I agree that your 4k monitors resolution and your Heaven settings are most probably demanding more power than usual. My aging eyes can't really discern the difference between 4k and my current 1080 x 1920 setup.
I'll post some pics I took of the setup later tonight.
Just a suggestion.