Collector's Edition Upgrade

[Felis]

I'm guessing you want to get the game because of the Steam sale but unfortunately I don't think you can't "upgrade" your current PC game using the Steam CE version. That would just add a second PC version to your account and the bonuses won't be added to your current characters.

It would not register a second PC version to the account, because every platform can only be registered once.

So OP, if you have already the PC version registered, buying the steam sale would do nothing for you (the CE items are in the CE registration key).