NEVER use software RAID on a mission critical machine. Recovery (I do that for a living) is difficult. A decent RAID contrioller will also monitor disk health. If you are going as far as using a real RAID controller, why not also buy a server-class system? Dell and HP both sell lower-end servers that are not much more cost than a PC. Then get the higher-end support for them – four hour turn around is usually the best support contract available. If its mission-critical, and you have already experienced crashes, you should be able to justify the cost to the bean counters. You IS will appreciate a server with a good hardware contract too.