As Spotify is discussed, WIMP is a obvious topic.
As WIMP is streaming in FLAC quality it would be great to have it integrated.
… unfortunately they don’t offer an API. It’s complete closed source … as an alternative ist “qobuz” to mention (qobuz.com) - but the service is young and their software not really stable (e.g. the Mac client crashes very often). But as I understood their policy, they offer an API. So if one will stream losless via Volumio, quobuz will be the selection.