Naim Unitiserve Music server upgrade suggestion

I am currently using a pretty out (and outdated) Naim Unitiserve connecting to a Western Digital NAS.  I guess reading files from a NAS is not ideal as the signal pass through many long cables and noisy, non-audio based components.  I have a very good APL DAC, so essentially, I want a very simple but audiophile quality transport with local storage.  The transport needs to be able to read and send native DSD signal out to the DAC.  And of course, most importantly, I am looking for better sound.  It seems most products pack more than what I want/need into one product. Is there such a thing as a digital transport?

Does anyone have experience with Naim UnitiServe and upgraded to another unit like Lumin or Innuos?  How does the UnitiServe compared to newer units?  I am quite interested in the Innuos Zen Mini or Zen at this moment.  Not sure if the mini can give significant improvement over the UnitiServe, or I should go with the Zen.