Adcom DAC

How would the Adcom gda-600 dac compare to some of the new DACs available today? Basic system, Rotel amp&pre-amp, Denon DVD and Von Schweikert speakers.
the gda-600 is ok for an entry level dac. i use the adcom gda-700 in my den setup. the 700 is another couple levels up from the 600. as for any 16 or 20 bit older dacs, i think a lot of them are better than some of the current 24/96 dacs. last time i purchased a dac, i listened to quite a few newer dacs and i ended up buying the audio research dac2 and a manley dac. i know somebody selling a 700 if interested.
Price? and is hdcd the main difference?
the 700 has hdcd, balanced outputs, better chips, and just sounds better. i used to also own the 600.
I just purchased a GDA-600. I know it's all relative, but it seems to have made quite a difference between my Apple TV and Adcom-565, 555II.

I do notice a very soft buzz/hum from the unit. Does anybody know if that is normal or is something wrong? The seller forgot to send me a power cord (which is on the way), so I just used an old cord from a Dell PC. Could that be part of the problem.
The Adcom was a decent entry level DAC 15 years ago. Technology has gone many miles since this unit was offered. Today most $100 USB DAC's are better.

For very little money you can do much better and get sound that was impossible when Adcom made the 600. Cambridge DAC Magic and Matrix mini-i are two that I would recommend.