If you want this kind of high-end, go to the big boys, and buy the whole "workstation. Often comes with video, SCSI, network, and case. Everything after that is optional (custom specced):
1-4 (or up to 8) CPUS
Memory
RAID controller(s)
Disks
Compaq, IBM, HP would be my recommendations for the Intel platform. If you're looking for *nix, it would be: Sun, Compaq, IBM, HP.
How much are you willing to spend? What is reliability worth? Do you have parts that you want to build into this?
--Woodie