I'll recommend Benchmark's DAC1 or DAC2. Both measure so incredibly well that it's difficult for me to imagine any other product being more neutral and detailed to any listener other than an analysis machine.
An old DAC1 can be often be found used for $550, too, so it's a good deal.
As said though, all DACs advertised as being for reference or studio use are going to be incredibly neutral. As long as you stay away from obviously colored units from audiophile companies (those units that have distinctly warm or bright sound signatures and are designed with listener pleasure as a higher priority than perfect measurements), you will do fine with any studio dac for audio mastering.
Edited by Timestretch - 1/16/13 at 4:11pm
