You can upgrade your normal account to a Collector's edition through the SE-Members account at a later date. If you want to preorder the PC version then you cannot link the CE items to that account since it is already registered with a non-CE registration code.

If you want the physical and pre-order items then you have to pre-order a PS3 version of the game and link it to the same account. If you only want the in-game CE items then wait until they announce they upgrade feature at a later date =)