I'm running my DX3P+ through USB from my desktop, and have two speakers hooked up via RCA which seems to be working fine. However, my question comes when I plug in my headphones and switch to headphone via the remote. I can switch between what seems headphone only "0-2" and headphone + Line Out "0-3". My question is, even if I unhook the speakers, the sound through headphones is pretty different between the two modes. Presumably both are using the DAC even though the "0-3" mode actually says "DAC" on the display and the "0-2" mode doesnt. What's causing this and which mode is better to use if I am just listening through headphones? Thanks!