Your correct on the pricing. I was thinking what Jim did might be higher than that. I hear you on the dac, as that was part of my original thought. However, upon reflection, it seems like finding a cheap, high quality Dac with volume control is pretty easy. If someone is connecting via a computer, they are likely using a usb dac such as Firefly or Meridian Explorer, so using their computer for level control. However, if somehow Jim could stuff all of this, along with dsp control into a bookshelf, that would be awesome!
I would note, if you include dacs for each unit, you wouldn't need rca or xlr inputs, just digital coax inputs (and an output) on one, linking it to the other.
I think at this point I will defer to Jim and see what he cooks up.