I read about Plextools and
CloneCD in CloneCD's help file. It stated in the FAQ that some Plextor CD-ROMs couldn't read the Subs when this software was installed. It could be a problems but I thought CloneCD had fixed the 'bug' so it should be ok. I don't know about the firmwares but I do know that reading has no effect on SafeDisc 2.
Plextor has blocked SafeDisc 2 writing but reading still works. This is because with SafeDisc 2 errors are skipped in the same way as SafeDisc 1. SafeDisc 2 comes into action when trying to write data to a CD-R.
Greets!