How good is Blue Sound Node 2 in WiFi vs Ethernet connection vs external CD player?

I find myself not understanding the OP.  The Node 2 has a built in DAC.  It's ok but nothing special.  If the Node is connected to your pre amp by the analog connects that is the DAC that you will hear.  If you connect it digitally to an an external DAC then the external DAC will be heard.  Which is better?  Devil is in the details.  If you have a stupendous external DAC, I would respectfully suggest using it.  If Said external DAC is a $39 Wal-Mart special, use the Node.  When in doubt, listen yourself and see which you prefer.
   Wired vs Wi Fi?  The manufacturer suggests wired.  That's what I use.  My wi Fi set up is somewhat dodgy, thanks to the incompetent folks at AT&T.

I find myself not understanding the OP.  The Node 2 has a built in DAC.  It's ok but nothing special.  If the Node is connected to your pre amp by the analog connects that is the DAC that you will hear.  If you connect it digitally to an an external DAC then the external DAC will be heard.  Which is better?  Devil is in the details.  If you have a stupendous external DAC, I would respectfully suggest using it.  If Said external DAC is a $39 Wal-Mart special, use the Node.  When in doubt, listen yourself and see which you prefer.
   Wired vs Wi Fi?  The manufacturer suggests wired.  That's what I use.  My wi Fi set up is somewhat dodgy, thanks to the incompetent folks at AT&T.

I purchased the Node 2 not as a stand alone, but as part of the whole house Bluesound system.  Arafiq  asks a good question .  I would point out that Apple is discontinuing Airport Express.  I have a second generation ATV and have tried using it as a digital transport but It sounded muffled in comparison to the Node; perhaps the current ATV  is better sonically.  
  The Node2 DAC is really pretty good,, considering the entire component sells for $500