I also use DACs in front of the Wiim and use a preamp to feed its RCA input. Would have loved a USB input, but happy with it the way it is… for the money spent. I mainly wanted the touch screen in my office, with voice control for Amazon Music, but it also works for many of my audio sources, as well. I just had to come up with some work arounds. As was mentioned, it means some digital to analog and back to digital conversion, but it still sounds good.
Wiim is giving themselves some room to grow for that next product, which is fine. If they add the same product with USB input and AirPlay, I would add it and move the ultra to another area of the house.