Addendum to the PS Audio UltraLink note above. Robert Harley, in Stereophile, loved this DAC. His "Conclusion" begins like this: "The PS Audio UltraLink offers many aspects of high-end digital processor performance at an unprecedented price. The product's soundstage transparency, focus, sense of air, and palpability have not been equaled at this price level, in my experience. Indeed, the UltraLink rivaled the $14,000 Mark Levinson No. 30 in these areas. Moreover, the UltraLink's resolution of transient leading edges and dynamics were superb by any measure. The overall presentation had much more in common with state-of-the-art digital processors than with comparably priced competitors."
However, this review dates from 1992! I've read several testimonies in this forum that remark on how much better DACs have got in recent years. If that's so, and the 32 year old UltraLink still sounds unambiguously better than a higher-end and fairly recent Marantz SACD player...well, the implication is that the OP would be wise to do what he's considering doing.