I'm aware that my tracks ripped for Sooloos won't directly work on Sonos, but am assuming that there's a way I can convert them without having to physically rip from the CDs again.
Sooloos is a NAS drive just like any other so you can map Sonos library directly onto the Sooloos library, ie same music library shared by both Sonos and Sooloos.
However there are two issues which depending on your circumstances may be non issues:
1: If you have any hi res files on Sooloos these will not be playable on Sonos.
2: If you ripped your files directly using Control:Mac/Control:PC, most of the important metadata needed to show track, album, artist info will not have been embedded in the files. If you ripped via third party app, ie dBpoweramp (plugin or otherwise), iTubes etc, and imported into Sooloos, this metadata will have been retained.
Without this metadata, Sonos will only see basic track info when browsing the files and not see tracks accessible via album, track or artist names. This will also be an issue if you reuse the rips in a different system although I believe that if you export from Sooloos this metadata may be reassembled - someone else can confirm.