I would dump half that memory and get more raptors. have bout 4 36gig ones in raid0, now that would be fast and you wouldnt have to mess around with SCSI.
or you could get 4 15K RPM SCSI's and RAID those up
I just entered in a corsair giveaway. They are giving away 4gb of RAM total, 1gb kits to 4 diff people. Don't particularly like corsair but whatever it's free
Sign up time already ended though so dont ask where to sign up