Raid 5 hardware almost always has an ASIC for each drive. The hardware on the typical mother board may say it will do raid 5 but it is still sharing the same ASICs. Also, any other devices connected to the controller will slow things down greatly. Most motherboards use one ASIC per channel (SATA 1 and 2, SATA 3 and 4, exc..). Same with IDE. If you are using a slow device on the same channel all devices on that channel slow down to the same speed as well as having to share the ASIC.
It is like comparing apples to oranges. If you want to run raid 5 or 50 you need to fork out the money for a raid controller, 1 ASIC per device. If speed is the only concern then go ahead and put one drive per channel on the motherboard (SATA) and use an IDE CD Drive and an IDE to boot off of. This will prevent any righting to the OS drive while keeping your stripe optimized. Unless you are using the RAID 0 purely as a work disk, stuff like video editing, I would NEVER suggest it. If one drive dies you lose everything and even the best recovery software short of a hex editor will be able to recover your data.
There are so many solutions out there that can fit whatever needs you may have; it is all a matter of how much you want to spend.
You do your due diligence and you will be much better off than trying to recover after a drive or OS failure. Plan for the worst hope for the best.