You could try Archipelago Remixed, I liked that almost as much as the original.
Personally my favourites are Archipelago and Selected Downbeats Vol. 1 which will probably stay as their best albums for me. Exploring The Tributaries is a little too plain and repetitive for me, altho it has a few great tracks in there. Echo is alot different then their later albums, borderline mix between dark ambient and psy, or that's the feeling anyway. Lime Structure was pretty nice but I don't listen to it too often. Their latest album Lungs Of Life however is a disaster for me, they are totally drifting away into some minimal progressive sound + they keep re-relasing old tracks on new albums. It's a shame.. but I still love them for their older work.