Hi,
I have been very fortunate to hear many dacs with my Rockna server. Two weeks ago we had a Nagra HD ($30000) dac traded in on the Rockna Signature dac. The Nagra HD was a very nice sounding dac but is now sold.
There are many people that purchase a Rockna WD Net server and keep their own dac. There are also many people that like the idea of a perfectly matching server and dac via i2S connection and a built in clock.
There is no wrong or right but instead just personal preference. I recommend people just play and have fun with audio. If you have a great dac that you prefer than keep it and build around that dac.
Cheers,