I was going to order the next expansion in line "Well of Darkness" but wanted to know if other expansions were more recommended.

If u intend to get ONLY one expansion, then Tome of Ice.

This adds brand new feat card system as well as monster devouring system. The other expansions only add new trap types, new hero and monster types and new items. Treachery system is introduced in all expansions. So if you only get one, get Tomb of Ice, which grants 2 completely new systems to the game.

Specifically in regards tot he criteria of 2-3 players, I don't think there's really any expansion that works better with that number of players. Although, come to think of it, Well of Darkness and Altar of Despair dungeons are best played with 4 heroes (5 players.) So if you regularly have fewer than 4 heroes on the table, and are unwilling to adopt an "always play 4 heroes no matter how many players" attitude (which many of us around here have already) then you'd probably want to avoid those two. So yeah, Tomb of Ice would probably be the best vanilla expansion for 2-3 players.

We have no problem putting 4 heroes on the table. I can easily have 2 players play 2 characters. Thanks to both of you.