Most important feature in desktop DAC/Amp : Mixer

My desktop is in my bedroom. Many times I want to listen to music with the PC off. Sometimes while working at my desk.

While off, I stream using a Logitech SB Touch. That's fine. And when watching lectures online, I can switch to my PC. What I cannot do however is mix the two.

I want to be able to listen to my Touch AND hear alerts from my PC.

Am I the only one??