Massdrop offers the S.M.S.L. T1 DAC / Tube Headphone Amp for $149.99 with free shipping. That's the lowest price we could find by $200. Deal ends December 9. Features include:

USB, optical, coaxial, and analog inputs

118 dB dynamic range

asynchronous USB transmission

PCM and DSD playback support

Note: It's expected to ship on January 19, 2019.