Need a DAC Recommendation.

+1 for the RME ADI-2 FS.  Awesome flexibility.

Border Patrol SE. Can get one used for $850. Sound wonderful and I may have one for sale. 

I too love my MHDT Orchid tube DAC. Sounds great and has great build quality.

We tried the Topping D90 against the SMSL M400 both in the same price range and preferred and bought the SMSL M400.  The Topping was a bit forward and bright for our taste, while the SMSL was just right.  Not as good as my Chord Hugo TT2 but much closer than I had ever expected for seven times less money.  Best DAC I've ever heard under $1000 although I'd admit I've not heard the R2R examples.
Happy listening!

I would put my money down on a Gustard X26 Pro. Easily beats the Topping everyone is so fond of, is built like a tank, has lots of settings and beats many much more expensive DACS on SQ. Extremely well designed.

I would buy it new.

And I would not spend much more than this considering DACs now-a-days have improved so much so that I would rather wait for a new technology before venturing any more money on one.