I would change source to a dedicated CD player such as Parasound CDC1500 I got mine new at auction for about $350 it use the Burr/Brown chipset that has become so popular. As for the Dac in your Pioneer or the Marantz, I would choose the one that you like the sound of better. After all its your ears that need to be satisfied in the end. I do agree with the others that the speakers are the most important. Have fun and happy listening.
What to do next???
My system consists of a Marantz Sr-8000 reciever, Pioneer DV-05 DVD player (also used for CD playback), and MB Quart QL S 1030 speakers with DH Labs T-14 bi wired cables and BL-1 interconnects. I am on a reasonable budget and am wondering what the best course of action is for the next level of listening quality and enjoyment. A new dedicated CD player? I'm looking to spend about $500 bucks. By the way, should I use the DAC in the DV-05 or the Marantz? Opinions? Scott