This is a 1st hand mac pro 4,1 upgraded to 5,1 through a firmware update. I actually did the processor and RAM (64 GB) upgrades (back in the day) myself, as well as adding the PCIe squid card with 4x 512GB AHCI PCIe drives (in raid to make 2 TB, Pic 3). It currently is booting off of the 750 GB SATA drive, but CAN (I forgot HOW to actually get it to do it) boot off of the 2TB RAID which should run at around 3500 MB/s or better.
This was a wonderful Mac for me, I just don't use it anymore. It is in great working order, and pretty darn clean. If somehow something doesn't work after shipping I would say to open her up and reseat all cards.
I do encourage offers, but I can't promise Ill go TOO low, I think after looking at other listings, this one is priced pretty darn fairly against them.