I think there is a belief that DACs have gone through huge improvements over the last ten years and the prices in the resale markets tend to support that. Honestly, if you audition something in your system and like it, that should be enough. A good product remains a good product three or four years later (or more). I'd argue that most of the "upgrades and updates" have little to do with sound quality and everything to do with marketing--especially when a lot of companies are asking for more than twice as much for the new versions than they asked ten years ago (or sometimes even less than ten years ago). I recently sent my Ayre CD Player back to Ayre for a new disc drive, because I still love the sound of my Cx7MPe 20 years after I bought it. Pretty doubtful that I would like the $5,400 CX-8 and more (and it's a LOT uglier).
If you like the Weiss, buy the Weiss.