I have just bought a TS109 as a backup for my Hifidelio. I have one directory for the Hifidelio backup (mostly FLAC files) and this is served by Slimserver 6.5.4 to my Squeezeboxes. I then have a second backup directory for my iTunes PC directory (MP3 and MP4 files) which is served by the built-in UPnP and can be accessed by any UPnP client such as my Nokia N770 device. This would seem to be the same setup as what you are looking for.

- Simon.