It depends. I'm sure you will have some argue both sides. The newer ones have the latest digital section, while the older ones have the better analog section. I personally prefer a older EAD, Sonic Frontiers, or Classe DAC to the newer MSB link III, et al. I think the analog section is the key to a good D/A convertor. The new $1K D/A's just don't have as good of a analog output stage as an older $4-7K D/A convertor. That of course is just my opinion, I'm sure you'll find some who disagree.
used high-end DAC or affordable newer model?
I have an old adcom 575 cd player that i will be using as a transport and i was wondering if it would be better to do with a newer dac like the MSB link III or Channel Islands VDA-1- or should i go used high-end such as the EAD dsp 9000 pro now on ebay- it seems that the older high end dac's can be had for the same money as the newer affordable models but what are the sonic differences?