[wgmontgomery]

"I think the DAC's inside the Denon 988 will do the job but the analog section my leave something to be desired in sound quality as compared to a high quality separate DAC."

+1 on that. If the DACs in your Denon are 24-bit/192-KHz, then (all things being equal) they are capable of better than "red book" CD quality (16 bit/44.1-kHz). Streaming music introduces a lot of other variables: format, streaming device, streaming source, etc.

HOWEVER, if the question is simply "are my DACs up to the task?" then the answer is yes. Again, all other things being equal (that's assuming an awful lot) you can expect CD quality...or better based just on the DACs.

 

[wgmontgomery]

Lots of info here, too:

http://www.audiostream.com/

 

[wgmontgomery]

"IMO the analog output stage and preamp are far more important..."

I agree, but I think that one of the reasons that DACs are such a popular upgrade is their low cost (compared to replacing a preamp, for example). You can spend mega bucks on a new DAC, but you can usually find a highly rated budget model.