The cheap mixer may be useful for something like output selection from a multi-channel device. I had my computer hooked up to my Nuo4 before I got my CDJs; had three outputs from the computer, and I could select what I wanted to listen to easily, especially toggle between headphones and speakers.

The actual functionality (with the Behringer) may be hit or miss, but at least you'll have a nice paperweight if you need it (or boat anchor, take your pick). Or, you could just use it to make a music video (AvB - Shivers; terrible video, but take a closer look at that mixer XD).