I really don't want to answer without knowing for sure what you're environment looks like and you've already done; what step are you at? Plus you're using technome's process, which is not how I've done it in the past. Do you have large SATA/IDE drive to mirror the current data drive to?
From the information you provided above, you have 2+ hard drives for the OS and 4 for "data". You want to replace the 4 data drives with 6 larger ones and configure them in a RAID5 with a hot spare?
What RAID levels are your current drives?
Do you have a backup of your current data drives that you have verified as containing everything you need to restore (or the mirror configuration set up as described by technome)?
When you get to the point of configuring the new array, I would shut down, replace the current 4 data drives with the 6 new ones and then boot from the smartstart CD and configure the new array.
Hopefully technome can give you more detailed steps.
Light travels faster than sound. That's why some people appear bright until you hear them speak.