Do you mean one that plugs into the AME interface, or an external app? I don't know of any plug-ins (Mainconcept makes one, but it's probably limited the same way), and if you're already doing this with the other two programs you listed, what do you need?
Yeah I mean an encoder that plugs right into Premiere, so I don 't have to export a sequence of images and then use a standalone encoder.
Got it. I don't know of one other than the Mainconcept encoder I mentioned: MainConcept™ Codec Suite 5.
Another option is to frameserve from CS5 to the external encoder of your choice. The frameserver isn't quite ready yet for release, but it's coming along. Read more about it here: How to frameserve from Premiere CS5?
Stay tuned to that thread for the "official" release.