You're welcome.
I forgot to mention that your SSD won't run in AHCI mode.
Of course the integrated S-ATA controller is capable to run in advanced mode which is very important when a user plans to hammer his HDD/SSD with many commands simultaneously, but for some reason HP disabled it in this generation of workstations (Z400, Z600, Z800).
The BIOS offers only two choices, RAID+AHCI or IDE mode.
RAID+AHCI means harddisks are always managed by RAID BIOS and only optical drives use the AHCI protocol.
If you plan use the Samsung Magician software, it will complain.
Anyway, I had a 120 GB 840 EVO in my Z400 for almost two years, it worked fine.
The DPS-475 CB 1A is a very good PSU from my personal experience, all my machines (three xw4600, one Z400, one d530 CMT) have this inside.
For the Radeon card the 650W is a better choice, especially cause it has two 6-pin PCIe power connectors.
Keep in mind that gaming cards are officially unsupported in these workstations.