DAC on Universal player

Is there a used DAC for $400 - $800 that would be an improvement over what the Denon's internal DAC's do?1

I don't think there is a usd DAC in the price range you just mentioned that would improve things enough to be worth it. I agree with the folks who said that modding the player will make the greatest improvement, and not only to redbook.

Sell the denon, buy the marantz universal (dv8400 or SA12v2). That will give you a very appreciable improvement on all formats for very little money. Denon doesn't make music very well at all with any of their players, they can only seem to get video right while leaving the musicality out....That said, if 2ch music is what matters most, having a DVD player in a seperate box is the only way to go if you have less then $6K to spend....

I recently purchased the Tri-Vista 21 and it made a marked improvment over my Denon DVD-3800. I now use the DVD-3800 as a transport most of the time exept for DVD-Audio. I think the biggest difference is in the smoothness of the midrange and treble regions. Also, the bass seems to be more solid and defined. To help you gage this response, I am in the middle of a major upgrade cycle so I still have a lot of tweaking to do to get things just right. Right now my system consists of...

Revel M-20
BAT VK-300x SE
REL Stadium III
Denon DVD-3800
MF Tri-Vista 21
Better Cables Digital Coax and SE RCAs
Kimber Kable 4PR Speaker cables

Hope this helps.
Dave

Arthursmack, you just beat me to it! I was going to ask the same question just about now. The only difference is that my universal player is Sony 999ES and my Pre-pro is Bryston SP-1.7.
I was reading good reviews about Channel Islands DAC with upgraded Power supply. There was one, modified by ModWright, for sale recently.($450).
I am wondering now, would it be an improvement over your Denon or my Sony? Regards.