As far as I
got it the task/question was to use the Cat5-cables for 
 analog
  music-signals (which is not a problem) and have a
digital (modified 
 or
  unmodified) WRT-router route the music to
different ports or to 
 produce the
  audio-signals on its ethernet-ports (which is a
problem, i.e. not 
 possible).
 Yes...thts exactly wat my question is, a wrt box which can play songs
 but since it doesn't have speakers i want to use cat5 as the transport
 media.
 Now my idea is to use the wrt as a decoder, an external DAC and the
 output of the DAC to the  speakers, and the question here is about the
 feasibility of such an arrangement, will it work?
 PS: have a look at this 
http://www.duff.dk/wrt54gs/ the author hasnt
 quite explained how he did the hardware part and thats wat i am
 interested in, albeit doing it a bit differently. 
 
he is using the fact that the WRT has a serial port. he writes the
sample data to the serial port, which is connected to a PIC that in turn
has a speaker wired up to it.
he is not doing real D/A conversion in the traditional sense.
i do not believe that you will not be able to find a D/A converter that
speaks a protocol that you can implement in software.
--p