R2R is just another way to skin the cats. DS is cheaper, smaller and does the same functionality with better quality in term of measurements. I haven't seen by any mean any quantifiable proof that say good implementation of R2R DAC beat the same league DS ones. That being said if you must stick to your plan, look for soekris DAC. By measurements it's pretty decent.
DAC Upgrade
I currently using a Bryston BDA-1 DAC and although it is a pretty good DAC, I want to upgrade to a 2r2 DAC. I recently purchased a Jays Audio cdt2 mk.ll transport and it is exceptional. My budget is in the $2,000 range and after careful review, I have narrowed the list to Schitts-Yagdrasil, Denafrips-Pontus and Holo Spring 2 level 2(new). Unfortunately, It is difficult to compare the three of them side by side, so I have to rely on expert reviews. I am looking for a DAC that is transparent, extended but smooth highs, 3D midrange and tight bass. My equipment is Prima Luna Prologue Pre Amp, Prima Luna Dialogue HP Amp and Silverline Sonata Mk.III speakers. Any thoughts?