I still can't understand why people continue to consider RAID 0 arrays for "performance".
Hard drives are by far the #1 "hardware" bottleneck in PC's today. Getting and extra 5% increase in performance isn't going to drastically change overall system performance.
RAID 0 - is good for taking 2 small inexpensive drives and combined them to make one larger inexpensive drive.
a. WD Caviar SE @200GB = $75 x 2 = $150
b. WD Caviar SE @400GB = $190 x 1
Save $40 in RAID - 0 while using another 20w from PSU adding heat and also taking up more space in your case.
RAID 1 - like mentioned above is excellent to secure important data incase of 1 drive failure.
So (a.) would still give you 200GB but it would secure the data
(b.) you'd be SOL if the drive fails.