Recently picked up Soundtrack Pro and Its is now my default Audio Editor.
Logic has a programable key-command to open an external audio editor, and Soundtrack Pro it is for me.
I've assigned [ apple key + U ] to open selected audio file in Soundtrack Pro.
This is interesting. What is it in Soundtrack Pro that you can't do in Logic? Are you editing loops, or actual full length tracks of audio? Are you editing stereo files? Groups of audio files? Can you select pre- and post-roll and location points and automatic play at preselected default locations?
You can see I'm looking for those same audio editing and transport controls!