I talked to a Sargent rep the other day and he said if I sent in my seat, they would custom make a seat out of the pan for around $280, depending on what I wanted on it. I am just not sure how much better the Sargent is, as I had one on my '86 Connie and it gave me butt burn after a while
I know Russell requires your seat to do a custom, and that is the best seat made for long distance riding. ON the Connie it wasn't that bad looking, but on the S3 it would be too big to look good. I know, my butt doesn't have eyes.
There are a couple of other guys who make custom seats, but they need your seat also.
This guy will modify your seat http://greatdaytoride.com/Home_Page.php
and supposedly it really improves a stock seat and he charges $75 and you pay shipping both ways. He is in Florida. I have seen some reports that it is really an improvement, some say no change.
I am not planning any mutliday rides until next year so I have some time to decide.