Well, if the workload intensity is not high then this device shall suffice. Of course, you can move the disks to the device keeping in mind that all the previous data on them will be wiped out.
By the way, if your data is large enough already, maybe you should consider a 4-disk model? If your data continues to grow this will give it more space in years to come, up to 9 TB in a RAID5 or SHR volume with 3 TB disks. Moreover, in this case, if you start with 2 TB disks, you won't have to replace them with larger ones until there are free bays - you'll just add a 3 TB disk to the 2 TB disks you've already put into the device and grow the volume to include the disk, then put another 3 TB disk and grow it again, and only then you'll have to replace the 2 TB disks with larger ones. Not necessarily all those in the same day, of course
This way you won't have to replace the 2 TB disks before their lives are over and still add more space to the storage.