I had not heard, nor hear of BLISS before your post, but after a quick listen, (I really like it) here's some I have that are similar:
Global Communication - "76.14" (this is very similar to "Quiet Letters")
The Future Sound of London - "Lifeforms" (Also similar)
Brian Eno - "Drawn From Life", and "Apollo: Atmospheres and Soundtracks", most of Eno's other "ambient" releases
Harold Budd - "Avalon Sutra" (less similar, but still ambient)
There are lot's more I have, but those are the first that come to mind.