All great choices mentioned, from the ones I've listened to at least. Arpe di Sabbia is definitely worth the second visit, especially disc 1.
I would add for consideration Spirals of Time- it's a two disc (?) epic journey of subtle, quiet power. There are a couple of nice pleasant surprises, one of which is contained in the last track.
Also Mare Vaporum- this is one that is basically a single, slowly evolving loop that does it like any of the best of Eno's or Roach's long form classics. It's not too simple though as it has a lot of moving parts and does meander at times from the basic loop, but it has a good mix of high and low tones and for me is one of his most hypnotic and relaxing albums, not a boring work but not overly dark or ominous either.