Node 2i use with external DAC

You will note a significant SQ upgrade moving from the Node 2i DAC to something in the $1500+ range for sure (e.g. Schiit Yggy, Benchmark DAC3, Chord Qutest).  In one of my systems I'm using the Node 2 to stream into a Benchmark DAC3 and it's a big improvement...but then again it should be at that price relative to the price of the Node 2 DAC.

My experience was that there was a noticeable, but subtle improvement in sound quality using an external DAC with the Node 2 (I didn't have the 2i).  DACs used were the Auralic Vega, Mytek Liberty, and the DAC in my Sony TA-ZH1ES headphone amp (which is very good).  

I obtained a much bigger increase in sound quality by replacing the Node 2 with a TEAC NT-505.  It has a warmer, more detailed sound, and has a much bigger soundstage.

If you're going to add a $1500 DAC to the Node 2i, you'd get more bang for you buck buying the NT-505 in my opinion.  It's about $2K and you can sell the Node 2i for $300-$400, so you might actually come out a few bucks ahead after selling the Node 2i.

Haven't heard the Gungnir but the Yggdrasil is definitely a big step up in performance from a Node 2i on its own.

The thing with the Yggy IMHO is that it's looking for balanced in and out to perform it's best so although the Node 2i works great the Yggy really deserves a better source in order to maximize its performance.

I did find that digital cables made a difference between the two components using both coax and BNC.

Gungy and Yggy are definite upgrades.
An Ayre Codex would be my choice on a budget
B

Gumby and Yggy would be a nice upgrade with the Node 2i. I used the Yggy for a while with the Node2i.

Also consider one of the Denafrips DACs. These are also an excellent value. I'm currently using the Terminator which is a definite step up from the Yggy, but isn't in the same price range. But from what I've heard, their lower priced DACs are quite exceptional for the $$$.