There are lots of benchmarks if you care to Google. If my memory serves, two basic SATA drives in RAID 0 should outpace a single Raptor 150GB. However, keep in mind that RAID 0 just about doubles the chances of data corruption and total data loss, both, over a single drive configuration. Then again, Raptors are obscenely expensive. If you have an excess of money to spend on hard drives, I'd go for two large disks in RAID 1.
RAID 0 just seems too risky for me. Maybe if you kept all your data on a third disk you'd be okay, but then your speed is compromised whenever you read or write from it.