Is it possible to copy several wav files as a session at once which would then have the same effect as a DAO, so without the 2 seconds, but with the advantage of being able to add more to the disk at a later time? If this possibility exist at all does it depend on the cdwriter or on the software being used? Right now that possibility is greyed out in CD creator 5. Any tips on the software?

No I don't think this is possible. You can either copy individual files with a zero second gap using the Disc At Once method or copy individual files withh gaps in the Session At Once Mode.

There will always be gaps when the SAO method is used since data will be written after the last track in order to let the software know where it can begin writing again.

To make an audio disc with zero second gaps I would use Nero (www.ahead.de). Drag the files to the left, select them and choose File, Properties. Here you can select the 0 second gap...

Greets