IMO, some of the best DAC's from 10-15 years back can still be very worth while acquiring. I think the price asked is the general decider, since some of the DAC's like you mention can now be had for a fraction of their original price, making them more than competitive with newer gear at a similar price point. If you pay for the current latest and greatest, then you probably get a superior DAC. Question is how much better to you? Nonetheless and without a doubt, the diminishing return factor will rear its head here.
