Humble Bundle has a lot of Sierra Games on sale

[cnikiel]

If you want to get a lot of the Sierra Adventures for only 11 Euro head over to:

https://www.humblebundle.com/games/sierra-the-3rd

Police Quest Collection
Quest for Glory Collection
Kings Quest Collection
Space Quest Collection

Have fun

[Graxer]

On top of that, the first two Gabriel Knight games and Phantasmagoria are included in the bundle and also supported by ScummVM (although, unlike the games you listed I haven't played them)!