You can upgrade straight to 1.06.
By the way, I think the Plextor 32x/12x/10x is only better for its Burn-Proof capabilities compared to the Plex124TS.
In 7 months of owning it I've not done one single CD-RW (CD-R's are so cheap ) and I believe that the SCSI interface is a lot more reliable than the IDE of the 12x10x32.
Maybe a future firmware will implement Burn-Proof for the 12x4x32, unless Burn-Proof actually requires extra hardware controlers !?!?... let me know.