My wife had her Act-3 upgraded to the equivalent of the Soundstage. Personally, I don't think it was worth it. Even after extensive time tweaking/setting things up, all the digital modes seemed extremely bass heavy. I guess that is not necessarily a bad thing for movies but you definitely would not want to use the DACs for music. The pass-through modes were also pretty "muddy" sounding. Musically, there was absolutely no comparison between using the 2 channel pass-through and a good pre-amp (a Marsh P2000b in this case). The Marsh was better in every possible way (tight bass, clarity, etc.).
At this point, we use the upgraded Act-3 just for movies and any time we want to listen to music we unplug it and use a real pre-amp.