Personally, I’d ditch the SAS drives; for $2150 you could buy 4x 10k RPM SATA Raptors ($700 total) and RAID 1+0 them, and then buy an extra 16 GB from OWC for $800-$1550, depending on which of their choices you go with. That’ll almost certainly give you a faster system for less money. If you decide that you really, really want to do SAS, consider buying one of Areca’s cards (bootable on Mac Pros) and using a cheap external enclosure. I’ve seen 4-drive SATA/SAS enclosures that aren’t particularly pricy. That’ll probably end up saving you money, and you can do it at any time, so you don’t have to decide up front. Plus, that’ll let you mix SATA and SAS, so you can throw a big drive or two into the system for Time Machine.

Personally, I don’t know what you’d do with 2×30″ screens, but whatever. Al Gore seems to use 3 of them, so I guess it’s possible. I swapped 2×24″ Dells for 1×30″ HP and I’m pretty happy, although I’d swap for 1×36-40″ if they were available on the market at a high enough resolution.

Just my 2 bytes