I'd do the 150 gig raptor with raid 1. Really if you are purchasing the raptor it's a little overkill to have a raid 0 array unless this is your test DB machine.
Think of a plan, what is the computer going to be used for? Gaming, multimedia, productivity, development, testing?
Personally I run raid 0 with a backup drive. If anything happens I just replace the hdd and image. If you are going to do multimedia or developing I'd go with raid 5, but again it's just me.
If you really want to spend some money get some 15k 72Gb SAS drives :twisted: