Don't do it!!!! I have a DNS-343 with my DSM-520. The MP3 ID3 tags are not being read by either the DSM-520 or the DNS-343. The files are all screwed up when you go to sort them in any logical order. In a nutshell, the UPnp AV server is not good on the D-Link NAS. Go get a NAS that is DLNA compliant. The D-Link might be compliant, but it is not good with the DSM-520. As for the storage and the GUI, it is great. But you are looking to eliminate having to have a computer running with a media server, well I hate to tell you this, but D-Link won't fix the ID3 tag issue on the UPnp AV server on the DNS-321(343). So you have to still have media server software running in the background on your PC to stream the Mp3's from your NAS if you want any kind of sorting for your music.
D-Link is well aware of this issue, but they have chosen not to fix it.