Yes it would, but there are other, in some cases simpler, ways to add more space
1) Buy two larger drives, set them up in RAID 1, and copy all the data to them. Remove the old ones.
2) Buy two drives, set them up on RAID 1, and put some of your files on the new volume.
3) If you are going to set up RAID 0+1, or 10 (slightly simpler), using the existing drives, you will have to back up all of the data currently in your system because putting the existing drives into another RAID set will cause them to be re-initialized and all of your data will be erased.
Right, thanks for the informed answer. I think I will have to go RAID 0+1 or 10. I have a mirror copy on my external hdd now so won't be a problem.