Just installed my stage 3 about a month ago. Had a hard time deciding as well on which firmness to get but glad I listened to the advice of others. Saw several posts where people who had stage 2 wish they had stage 3 but didn't see anyone who felt it was a mistake to go with 3 to begin with.
My initial driving response was that it felt almost too firm. But I was only comparing it to the loose and sloppy feel I had in my original box. After a couple of drives, I couldn't be happier with the way it feels.
