I got near realtime encoding on an AMD XP 2600 with a 333mhz bus. I was encoding 30 second clips with a 5 second voice over and overlay at the end. The source video was mpeg-2, so it probely would of been almost real time if i used DV as the source.
OK, your 2600 is "almost" real time. That means the 2000 mentioned in the original post would not be. As you get to the 3+ GHz range, you should have a MUCH better chance.