Nah, that would took too much time and also mostly it would work on single NAS Manufacturer and Firmware
not if you do linux, many nas support linux based apps/plugins
readynas, use an embedded version of debian for example
@ others, its not a UPNP but is linux based and may work on some nas, is nifty try @ http://www.subsonic.org
i use to stream to my android phone over 4g, directly from my readynas
the only thing I miss from mediamonkey is auto-dj/last.fm dj
@ peke, is/will/should UPNP be gold feature only?