Experience with Bluesound Node 2 use with external DAC

I am very impressed with the Node 2.  So far my use of the Node has been with it's built in DAC.  It sounds great.  Since I don't own an outboard DAC I have had no other choice but to use the Node's DAC.  It is hard to fault it's DAC at any price much less the $500 price of the Node.  That being said, I realize there are alternatives out there than can improve upon the built in DAC.  I am at a point now where I am curious to hear what an external DAC may have to offer in terms of sound quality.  For those of you who are running a Node through an external DAC, what would you recommend and what type of improvement have you experienced vs DAC in the Node.