2 DACs: 1 best for movies, 1 best for audio, why?

I have a home theater system integrated into my 2-channel system. pre/pro connects to pre-amp using home theater bypass input on pre-amp. I have a dedicated 2-channel DAC and transport. I have a BRP/DVD going into the pre/pro as well as FIOS TV. Then, here comes the dilemma: I have an AppleTV that I use as both a music server, and sometimes for video. The AppleTV has an optical out. I can send that output to either the pre/pro or to the 2-Channel DAC. What's strange is that the AppleTV sounds better on video when I send it to the pre-pro, but it sounds better on music when I send it to the 2-channel DAC. Movies (voices, sound effects) don't sound as real through the 2-channel DAC. Similarly, music doesn't sound as real through the pre/pro. Any thoughts? Note that this is not a 5.1 verus 2.1 issue: I am comparing 2 channel video to channel audio.