Best DAC under $ 2,500 on used market

I have been looking at Esoteric cd players.....X series, DV-50 etc... I have a McIntosh 751 cd transport with the Esoteric die cast clamp and an rca output. What outboard dac's could put me in the performance range of an X-03 or so?
I am biased towards baas extension, bass power and dynamics.
Thanks for your advice.
Bill