"Zd542: So in your opinion, a DAC isn't needed as long as I mostly play 256/320kbps files from iTunes?"
Maybe. I think a better way to put it is that you will get more out of a new dac if you are feeding it better quality music. Even playing mp3's through a new dac, though, will probably sound better just because of the fact that the analog portion of the unit will be of a much better quality.
In my first post, I recommended that you try bypassing the preamp section of your NAD. I would try it if you haven't already done so. Seeing how big the difference and what the difference is, may give you some insight on how to proceed.
Maybe. I think a better way to put it is that you will get more out of a new dac if you are feeding it better quality music. Even playing mp3's through a new dac, though, will probably sound better just because of the fact that the analog portion of the unit will be of a much better quality.
In my first post, I recommended that you try bypassing the preamp section of your NAD. I would try it if you haven't already done so. Seeing how big the difference and what the difference is, may give you some insight on how to proceed.