Running Dual HdPlex's

[Mmbrock1]

So I am building a case atm for a atx full size, but the goal is it make it think as possible and as short as possible. 
So I started looking on doing external power supplys. HdPlex 400w but using a 330w brick.

But I do not believe 400w is enough. So What if I use two of them. one for the main parts other than the gpu, And use the second one for the gpu.
Yes I know dual powerbricks... blah blah blah. 
And im guessing you have to short the connection on the HdPlex 400w to use it for just the GPU.

the build is 

 

CPU:e5-1650 6c/12t
MOBO:MSI X79A-GD45

RAM: 2 sticks of Hynix 16GB PC3L-10600R DDR3 ECC (1333) (32gb)
GPU:PNY NVIDIA GTX 1080 8GB XLR8 

SSD:120GB Hp 

CPU COOLER:EVGA CLC 240 Liquid

CASE:EVGA DG-76 Alpine White Mid-Tower
PSU:CORSAIR HX Series Semi-Modular HX850 

would love to here you're thoughts of this.

[iRileyx]

I'd just use an SFX power supply in the case to be honest.

 

It will make the case a little bigger(not by much as SFX psu's are pretty small) and would actually take up less total desk space than having to butcher 2 external PSU's together.

[TheRandomness]

You could either use an SFX PSU, as stated above, or possibly a TFX PSU. I mean, your idea would work (and yes you’d need to short the PSU, or use a MOSFET over the PS_ON and GND connections, with the other leg tied to a 5V source from the motherboard to get the PSU powering the graphics card to turn on by itself).