I have all versions,each is outstanding and for a different mood.
The 7 hour version is the one to get.You can find the full download in lossless FLAC here-http://www.musiczeit.com/album.php?album=164&Robert+Rich+Somnium
This site also has many of Robert's other titles,including some wonderful live concerts.
I have the DVD which does play in any player and some high end CD players.It came out way before the download.
The Itunes version is OK but very edited,proper for quick naps.
The Itunes App is most likely the best version as it can continue forever,a very cool idea.It does not have anywhere near the sound variations of the DVD but has I think 5 loops that can morph from slow to slowest.
Of course,the audio quality is also quite low on anything Itunes.For me,it has to be lossless.
This music is designed to be played at very low levels so do not crank it.It should be barely audible as you drift to sleep.