Seabourn is our preference, but no one seems to do the itinerary we actually want - to include Antarctica (actual Antarctica, not a sail by - so, expedition ship) and the Chilean fjords. Sometimes Seabourn does a repositioning on the last cruise of the season - one goes up the east side to go to the Arctic for the summer and the other goes up the west side of South America for Alaska. Haven't seen anything similar on an Atlas itinerary. 2028 just starting to be released so keeping an eye on all of them (Seabourn came out yesterday for past travelers, middle of August for everyone. But fares haven't been uploaded yet)

We're usually last minute/what a deal sorts of cruisers (since we do it to see new places the first time, or places that are best/only seen by sea) and planning this far out is sort of wild for us. But necessary - there aren't a lot of sailings in this area and it's popular, they sell out pretty quickly it seems.