DAC on Universal player

Yeah, what Sean said....but, not SACD because, I dont believe the 2900 can output SACD in digital.

If all I'm trying to do is get smooth sound on redbook, wouldn't it be cheaper to pick up a Cal Labs Ikon MKII or Shanling CDS-100 and strictly use it for that?

Yes a DAC can improve your redbook, but will definetly do nothing for SACD as this is output , only from the analog outs of your Universal Player.

what DAC's would improve the redbook on a Denon2900?

I would have said the Tri-vista 21 which might be a bit steep for your taste or not. I was looking at the same solution as you, that's why I was drawn to this thread. I am interested in SACD as well as good redbook playback which seems to be a nomenclature at this point. The trivista SACD appears to do both well but at 6.5K. I have also been looking at alternatives, and thought this might be a solution.. Use a DAC to get reasonable Redbook performance. I just read a link about a guy who bought the new 9000 Sony SACD and the tri-vista 21. He could tell little difference with it in and out of his system (the tri-vista)... a little disconcerting... I hope we get more responses to your query... Real world examples would be nice...