Add my voice to those recommending the Dodson DA-217MkII-D. As I described on another thread, I bought one here on AudiogoN to upgrade the sound of my Denon DCD-1650AR. I was happy with the Denon as a transport, but I wanted to improve the resolution and the sample rate. I initially planned to get a Bel Canto DAC2, but I wasn't happy with the physical layout. I am a retired electronic engineer, and when I read about the Dodson, and the design techniques that Ralph Dodson (another retired electronic engineer) used, I decided that this was the DAC for me.
Adding the Dodson, via a Harmonic Tech Magic Digital One RCA cable (which I also bought here on AudiogoN), made quite a difference. The sound became much more focused and transparent, while at the same time smoother. The sound stage expanded, and the localization of individual instrumental voices in the orchestra became much more precise and consistent. There was also a notable increase in the dynamic range.
I had some questions about the unit after I bought it, and I called Ralph several times. He was always gracious and helpful.
As an outboard DAC solution, the Dodson DA-217MkII-D worked well for me. I recommend it highly.
Good luck!