Hi please find the hp tested power supply upgrade options on this unit:
Power Supply
475 watts wide-ranging, active Power Factor Correction, 85% Efficient
The Z400 475W power supply efficiency report can be found at this link: http://www.plugloadsolutions.com/psu_reports/80PLUS_DELTA_DPS-475CB-1%20A_475W_Report.pdf
(Optional) 600 watts wide-ranging, active Power Factor Correction, 80% Efficient
This power supply option has been discontinued on Z400 as of June 30, 2012
The Z400 600W power supply efficiency report can be found at this link: http://www.plugloadsolutions.com/psu_reports/DELTA_DPS-650LB%20B_ECOS%202171_600W_Report.pdf
Hp tested Graphics upgrade options as given below,
1.Professional 2D
NVIDIA Quadro NVS 295 256MB PCIe Graphics Card
FY943AA
NVIDIA NVS 300 512MB Graphics
XP612AA
NVIDIA Quadro NVS 450 512MB Graphics
FH519AA
2.Entry 3D
NVIDIA Quadro 400 512MB Graphics
LD542AA
NVIDIA Quadro 600 1GB Graphics
WS093AA
AMD FirePro V3900 1GB Graphics
A6R69AA
AMD FirePro V4900 1GB Graphics
A3J92AA
3.Mid-range 3D
NVIDIA Quadro 2000 1GB Graphics
WS094AA
NVIDIA Quadro 2000D (Spec DVI only card)
A9C88AA
AMD FirePro V5900 2GB Graphics
LS992AA
3.High End 3D
AMD FirePro V7900 2GB Graphics
LS993AA
NVIDIA Quadro 4000 2GB Graphics
WS095AA
NVIDIA Quadro 5000 2.5GB Graphics