There are two solutions. The easiest is to use a DLNA control point app pointed at the dac+ DSP. I'm using BubbleUPNP but there are lots of others. The second is geekier. Add the UPNP plugin to mpd.conf, comment out the database directory, and enable port 6600. You can then use an MPD client--I use M.A.L.P on Android--as a front end. Set up a link to the ip address of the PI and you have access to the files on your DLNA server.
Either way you now have access to the DSP functions of the OS and the ability to browse music on a NAS or other device that runs a DLNA server. I have had no luck setting up my NAS as an mpd source and prefer to browse by file anyway.