why would you want an older DAC, there is no upside in that? Since DAC's are 95% technology, and prices have really fallen, I would suggest you get a new one and take advantage of that.
Some very reasonably priced ones are: MHDT Labs Paradisea, Cambridge Audio DacMagic
Some very reasonably priced ones are: MHDT Labs Paradisea, Cambridge Audio DacMagic