I would question the need for RAID. Yes, it will be faster. But do you need faster than a good modern 7200 rpm SATA HD?

The downside tpo a mirrored RAID is expense and double the risk of failure (although you should back up anyway...).

The other problem with motherboard based RAIDs is that if your motherboard dies after production of that model has ceased then you will not be able to access the data (but then again, if you have been back ing up...)