Guess I can also give you a hand on this, to be honest.
I'd also go with a sound capture and recorder program to save Spotify streaming.
These are more reliable since you merely record and save streaming music from Spotify and you do not download spotify music streams straight from them. So if spotify streams get tweaked you'd still be able to save spotify music without any issues.
Anyways, if you want you can also take a look at some Audials Tunebite app:
This one,among other things, comes with a built in spotify recorder and is able to capture record and save spotify streaming music to your hard disk fast and in pretty good quality.
Plus it also works to convert spotify to mp3 or whatever formats you need for easier playback, that's gotta come in handy.
I say it's worth checking out, might solve your problem with how to save Spotify streaming music for offline listening on any devices you need.