I just had my Herron VTSP-3 upgraded to the VTSP-3A.
The improvements are quite significant, not subtle at all. I really found it hard to believe that the overall performance of my VTSP-3 could be improved this much as I was quite happy with the sound before.
The sound stage is now deeper and the overall sound is much richer with greater detail - the layers of the onion have been peeled away. It is as significant as going from a CD to an LP - improved resolution, sound staging, imaging and dynamics - an overall quantum leap ahead. With high resolution media my system now comes frighteningly close to simulating a live performance, a goal we all pursue.