Yup, your new controller does not have to have just one RAID container on it. I would pretty strongly suggest that you not "burn" the 100GB/drive by creating a "mixed" raid5 array.

Learn the characteristics of RAID 10 and RAID 50, and which RAID level is appropriate for your app. I/O and protection needs contribute to your RAID choice.

RAID5 is easy to work with, especially since you know exactly what disk is dead. All you need to do is power down the array, replace the dead drive, then power the array back on. The parity info ...

The maximum number of drives in a RAID 5 set is in theory unlimited, although your storage array is likely to have built-in limits. However, RAID 5 only protects against a single drive failure.