Question about chassis + PSU

[uktz]

I currently have a CSE-846E16-R1200B (with a LSI 9211-4i & BPN-SAS2-846EL1)

 

I was considering dropping a 3900x build into it, but noticed that that I might not be able to fit a full modular power supply into it. Does anyone have this case, and were you able to fit a full size PSU into it? (Example: Corsair HX850) or should I just use the built in power supply (2x1200w) that came with the case?

 

Full build

1. Processor: 3900x
2. RAM; 64GB 3600mhz / Up for discussion - Possible ECC memory slot
3. Power: Corsair HX850 // 2x1200w Gold+
4. Motherboard: ROG Strix x570-E / Up for discussion - looking for an AM4 ECC-supported motherboard
5. Controller: LSI 9211-4i HBA JBOD FREENAS UNRAID
6. Backpane: BPN-SAS2-846EL1 24-port
7. Case: CSE-846E16-R1200B
8. MAYBE: 1080Ti -- I only glanced at the wires stemming from the power supply shroud, but I didn't notice any 8pins. Does anyone have any suggestions if I wanted to add a graphics card to the server for passthrough/encoding?

 

[uktz]

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