Continuation from here: http://h30434.www3.hp.com/t5/Business-PCs-Workstations-and-Point-of-Sale-Systems/Z800-Upgrade-for-2015/td-p/5067136/page/3
Many Thanks to all the people who helped!
I installed the Intel 9.6.0.1014 driver as suggested however, it replaced a newer driver 11.1.0.1006. It may have worked without installing the older driver but I errored on the side of a known working solution.
The real source of my problem was that I needed to enable "Option ROM Download" for Slot 1 where the PCIe card was plugged in. Once I got that set, after restarting, I could see the drive and set it first in the boot order. What does "Option ROM Download" do?
BTW what does "Compute" enable do? The reason I ask is that I have a nVidia Quadro 6000 which I can select to use the 6Gb ram for graphics and compute needs. Do I need to enable "Compute" on that slot to make it work?
So, once I got this PCIe SSD drive working
https://eshop.macsales.com/item/OWC/SSDACL6G.S/
I decided to give my original purchase, the 480GB OWC Mercury Accelsior PCIe SSD (2x240GB RAID 0) a try and it worked!!
Thanks again for all the help!
FYI During my conversation with OWC I was lead to beleive the newer version of the dual SSD RAID 0 is aslo AHCI. My understanding is that it should work also since it can uses the same SSDs. The technical staff there was very helpful.
https://eshop.macsales.com/item/OWC/SSDPHWE2R960/