FileBot

Pretty much every post in this forums is about this, just not Sabnzbd specific

The amc script does everything:
http://www.filebot.net/forums/viewtopic.php?f=4&t=215

Now you just need to figure out how to integrate that with Sabnzbd.

1. Tells you it's a cmdline tool:

since filebot/amc is really just a cmdline tool you can probably make it work with any software that can run external programs, or just call it every once in a while with scheduler or cron.

2. Shows you a video how it is just a cmdline tool:
http://www.youtube.com/watch?v=brGyo2uQzSs

If you can't call a cmdline tool on finished downloads though that's bad. Alternatively you can use some sort of scheduler but calling filebot on complete would be much better.

Are you sure calling external scripts is not supported? Almost any download tools should allow this since it's easy to implement.

EDIT:
http://wiki.sabnzbd.org/user-scripts

Sorry, I don't use Sabnzbd but it sounds pretty doable. You can ask in their forums for details.

If you figure it out please share it with us here as well.