I have the same bike as you, from 2003, with thousands of touring miles under the wheels, so I understand what your ride is like. The Atlantis really rides its most comfortable with a load. A couple of years ago, I had a ride (perhaps a couple of hours) on a current model, long wheelbase Atlantis. The shop knew I rode a 58, 700 wheeled version. After doing a few measurements, they set a demo up & had me give it a go. Right away, I felt it rode "better" in terms of comfort, taking the speed bumps in the ally with no drama. Later, we were out on some local trails, challenging but no technical. Even on tight turns, it handled just like my own bike. In short, Rivendell had improved the ride quality noticeably, and hadn't sacrificed anything in handling. On return from the ride, I found out it was a 53 cm in their newer sizing system. I'm not sure what wheel size they are using these days.
dougP