Hi, the new 74GB drives are relatively small by todays standards. Are you limited in the capacity that can be used?
What benefits are you trying to achieve by using Raid 0?
Do you really need a Raid setup?
Excluding disc failure, it is only likely that the drives with the operating system installed thereon, are likely to become corrupt, necessitating a reinstall of the operating system. By moving or reinstalling all programs and data to alternative drives, you will free up disc space on your current Raided drives.
Basically, I am not sure what you are trying to achieve with your current setup and use, so it is difficult to advise one way or the other at the moment.