Both
At the moment, I have the Zen DAC v2 hooked up to my windows box, and the Tone2 Pro to my MAC. The reason is that Apple does not yet offer a Apple Music client for windows that will stream lossless. Otherwise I would have no need for the tone 2 pro at home, and it would be in my office at work.
1) There is no noticeable difference sonically running RCA or balanced, especially when all paths lead to the CAN.
2) Balanced is running from the Zen DAC to the CAN. RCA from Tone2 Pro to the CAN.
3) The benefit of this setup is that if I can switch with the press of a button from the balanced input (Zen DAC v2) on the CAN to the RCA input on the CAN (Tone 2 Pro), and leave everything else connected without getting messy or complicated. If I want to listen to Apple lossless, hit a button, start listening, and vice versa back to Windows.