Yes, i keep thinking a Raid-0 setup with 2 small 36g WD raptors 10k drives rather than 1 15k sas scsi.
For a order entry machine or even as a charting machine 2 36g drives will be plenty. The older IBM intellistation scsi drive at 18g was always just fine. Big hard drives are for pictures and stuff like that, not for my style of trading.