Just my humble opinion, don't go with RAID if you just want speedy drives, unless you are willing to take the data loss risk involved with RAID0. For the money you'd spend on multiple drives for a RAID array you might be better of just buying a single large SSD or a WD Velociraptor. Compare the price of your multiple drives for your RAID to the cost of a 256GB Samsung 840 Pro Series SSD at $250USD and the cost of the 500GB Western Digital Velociraptor 10,000rpm mechanical drive for $150USD. I bet the price of the SSD and Velociraptor are cheaper than the multiple drives for your RAID array and would most likely give you better performance; especially the SSD.
But if you are hard set for setting up a RAID, I wouldn't do a software RAID...