I am looking for a smoothest sounding outboard DAC

I also own the Audio Note 3.1 Balanced Dac, and it is superb, if your budget permits. Joe at JC Audio can set you up with any Audio Note stuff you need.

Re: the above post, in fact, I just ordered a Spectral SDR 3000 transport to mate with it (will be doing a shootout soon with some other transports- too bad I don't have a CEC to add in the mix!)

There's a Timbre TT1 Dac on here now for $645, which is a steal. An oldie but a goodie, and super smooth.

Wadia 27 would be excellent.

Kora Hermes tube dac. Dynamic, liquid, rich and very, very smooth. I owned Bel Canto Dac 2 before and the Hermes walked all over it. The best dac south of $4K I've ever heard.