I don't think you need to Raid SCSI. It's fast enough as it is.
I have the
Adaptec PCI 29320A-R SCSI Controller
Seagate 73GB 15k Cheetah SCSI ST373453LW
Both can be found on Newegg. It's what I'm using in both my systems in the sig below, and they both fly. When playing CS:S, I'm always the first one to start the game, even when the timer starts from 5 and they guy says, "Alright, let's go." I'm in front of everyone else.